Bear with me. Some of the below is driven from need, rather than want and is a bit of a ramble. Thought I'd think out loud and join the throng of others considering the same.
I love(d) my 5D3 and L Zooms + other lenses and a spare 7D2. Still do, but my drivers for owning FF gear have changed (and it's so big/heavy....). I was keen enthusiast, on the brink of turning Pro as I left the RAF in 2015, did a few paid jobs, but decided ultimately getting paid from regular employment and keeping Photography as a hobby rather than work was my best option. It was the right gear at the time for my plans then - Studio/portraiture/weddings along with my own interests of landscape/travel. I'm still a massive enthusiast, and not ashamed to say I also like the gear (hence want vs need).
Fast forward to now. I have reached a decision point and decided I had too much money invested in Canon equipment than was rational given the levels of use it was getting as a keen enthusiast and I do mostly Landscape and travel these days. I think Canon's launch price of £3600 for the 5D4 catalysed this thought process. Used values of 5D3 down to about £1200, and even with part ex bonuses etc, you are still looking at the thick end of £2000+ to upgrade a body. Which is a bit spendy for an enthusiast (well it is for me). Granted, prices are already beginning to soften on the grey market (£2.7k or so), and that's evil initial depreciation for some!
Anyway, to cut a long story short, through a process of rationalising, and thinning down of kit, spare body etc, I'm faced with a choice of upgrading my 5DIII to a 5DIV (and refreshing my core lenses, while disposing of others) for a net cost of +£50 or so. That's an attractive option from the desire side and would leave me with 5DIV, 16-35 4 IS, 24-70 2.8 II, 70-200 II. A really solid trinity of zooms and a beast of a camera.
On the need side, I can get a Fuji XT-2, 18-55, 10-24 and 55-200, and if I took an alternate path from the above option that involves getting rid of all the Canon gear I currently own, I'd end up with around £3k in the bank and the Fuji setup described. That leads to the devil in my ear saying £50 gets you tech refreshed into a 5DIV with top notch lenses, and the angel in the other one saying come on, over £3k in the bank. Is the Canon gear really £3k better (for your needs) than the Fuji? Do you really want to lug another heavy FF DSLR and big lenses around? Will you use it as much as if you had a lighter system?
I can make a case for either. I'm a gear nut, I'm never happy unless I've got the latest, and best. The 5DIV rig will be awesome, and it's a sunk cost - I've already found the money in the past (all bar £50) for this hobby.
The Fuji is technology evolved - it shows how fast and effective mirrorless is becoming. It (appears) to be an excellent camera, if I "compromise" on the lenses per the above, I still get a very nice set up. However, if I went for all pro lenses to replicate what I have now, there would be no fiscal case for a nuclear option to switch to Fuji. Well, I'd be about £500 in the bank better off overall.
So really my dilemma is do I downsize or not. Especially given that the downsized gear, through the progress of technology, is really now very very good so not so much a compromise as it might otherwise have been. The sensor on the Fuji seems to do very well - good dynamic range, low noise, good resolution, and a fairly strong system built around a very compact SLR like body. I don't see a downsized route in the Canon that gets me the size advantage of the Fuji system. Would it be a 5DIV and 2.8 L Lens replacement - no, of course not. Would it be good enough given advances in the State of the Art - many seem to think reading online. I'd be interested in your thoughts.
On a related note, I'm increasingly of the view that mirrored cameras are at the end of an era. The state of the art with mirrored cameras is excellent, but rapidly being undermined by the upstart mirrorless cameras. A bit like Plasma vs LCD vs LED vs OLED. I strongly suspect that within the lifecycle of the 5DIV, the advances in mirrorless will be such that there may not be a mirrored 5DV. Not that any of this matters that much - a bit maybe from a depreciation standpoint. Cameras are never an investment of course, but if the market shifts to smaller, formats, demand drops, and in some cases through the floor. We are kind of seeing that with 5DIII used values. Who doesn't prefer smaller, faster, lighter, cheaper etc. I know the camera you have in your hand is the one that matters and while you decide, you aren't taking pictures - I get that, but I've never before had this level of paralysis over buying new gear. And before you say, so keep your old stuff, I haven't ruled out that option entirely!
I love(d) my 5D3 and L Zooms + other lenses and a spare 7D2. Still do, but my drivers for owning FF gear have changed (and it's so big/heavy....). I was keen enthusiast, on the brink of turning Pro as I left the RAF in 2015, did a few paid jobs, but decided ultimately getting paid from regular employment and keeping Photography as a hobby rather than work was my best option. It was the right gear at the time for my plans then - Studio/portraiture/weddings along with my own interests of landscape/travel. I'm still a massive enthusiast, and not ashamed to say I also like the gear (hence want vs need).
Fast forward to now. I have reached a decision point and decided I had too much money invested in Canon equipment than was rational given the levels of use it was getting as a keen enthusiast and I do mostly Landscape and travel these days. I think Canon's launch price of £3600 for the 5D4 catalysed this thought process. Used values of 5D3 down to about £1200, and even with part ex bonuses etc, you are still looking at the thick end of £2000+ to upgrade a body. Which is a bit spendy for an enthusiast (well it is for me). Granted, prices are already beginning to soften on the grey market (£2.7k or so), and that's evil initial depreciation for some!
Anyway, to cut a long story short, through a process of rationalising, and thinning down of kit, spare body etc, I'm faced with a choice of upgrading my 5DIII to a 5DIV (and refreshing my core lenses, while disposing of others) for a net cost of +£50 or so. That's an attractive option from the desire side and would leave me with 5DIV, 16-35 4 IS, 24-70 2.8 II, 70-200 II. A really solid trinity of zooms and a beast of a camera.
On the need side, I can get a Fuji XT-2, 18-55, 10-24 and 55-200, and if I took an alternate path from the above option that involves getting rid of all the Canon gear I currently own, I'd end up with around £3k in the bank and the Fuji setup described. That leads to the devil in my ear saying £50 gets you tech refreshed into a 5DIV with top notch lenses, and the angel in the other one saying come on, over £3k in the bank. Is the Canon gear really £3k better (for your needs) than the Fuji? Do you really want to lug another heavy FF DSLR and big lenses around? Will you use it as much as if you had a lighter system?
I can make a case for either. I'm a gear nut, I'm never happy unless I've got the latest, and best. The 5DIV rig will be awesome, and it's a sunk cost - I've already found the money in the past (all bar £50) for this hobby.
The Fuji is technology evolved - it shows how fast and effective mirrorless is becoming. It (appears) to be an excellent camera, if I "compromise" on the lenses per the above, I still get a very nice set up. However, if I went for all pro lenses to replicate what I have now, there would be no fiscal case for a nuclear option to switch to Fuji. Well, I'd be about £500 in the bank better off overall.
So really my dilemma is do I downsize or not. Especially given that the downsized gear, through the progress of technology, is really now very very good so not so much a compromise as it might otherwise have been. The sensor on the Fuji seems to do very well - good dynamic range, low noise, good resolution, and a fairly strong system built around a very compact SLR like body. I don't see a downsized route in the Canon that gets me the size advantage of the Fuji system. Would it be a 5DIV and 2.8 L Lens replacement - no, of course not. Would it be good enough given advances in the State of the Art - many seem to think reading online. I'd be interested in your thoughts.
On a related note, I'm increasingly of the view that mirrored cameras are at the end of an era. The state of the art with mirrored cameras is excellent, but rapidly being undermined by the upstart mirrorless cameras. A bit like Plasma vs LCD vs LED vs OLED. I strongly suspect that within the lifecycle of the 5DIV, the advances in mirrorless will be such that there may not be a mirrored 5DV. Not that any of this matters that much - a bit maybe from a depreciation standpoint. Cameras are never an investment of course, but if the market shifts to smaller, formats, demand drops, and in some cases through the floor. We are kind of seeing that with 5DIII used values. Who doesn't prefer smaller, faster, lighter, cheaper etc. I know the camera you have in your hand is the one that matters and while you decide, you aren't taking pictures - I get that, but I've never before had this level of paralysis over buying new gear. And before you say, so keep your old stuff, I haven't ruled out that option entirely!