It might just be me but if you've never used a 45 prism, it might be an idea to have a go with one before you buy.
I couldn't get on with it at all, it felt awkward, half way between a straight one and a wlf, neither one nor the other, I was the same with a chimney.
Its not much of a problem in a studio setting when you have set up time on a stand or tripod but out in the field on the hoof a 45 felt like a bit of a fight to use.
I find the 45deg to be easy to use and focus out and about compared to the WLF, which even with a 'bright' screen is a bit dim for focussing without the magnifier
I ended up getting the PM5. I want this for studio work with camera on tripod, I prefer to use a meter in the studio. Out walkabout I will use the it the conventional way looking down from the top