Canon 70-200 or Canon 100-400

[raider2727]

I am just about to return to Canon from a brief spell with Nikon.
In the past i had a Canon crop body and along with a 24-70 i had a 70-200 f2.8L non IS.
I am now returning to Canon with a 5D MKII so full frame.
My dilema is will i be better off getting a 70-200 and 1.4 Extender or go for the EF 100-400 or something else?
I used the 70-200 as a general tele, odd distant portrait but mainly for trips to the Zoo and Wildlife park
I am even considering the Sigma 100-300 DG f4

Any thoughts on this or other suitable lenses?

[Canon Bob]

There have been more than a few unhappy relationships between pump action zooms and full frame sensors....you're 2.6x more likely to put dust on your 5D2's sensor than a crop sensor.

Bob

[ShrubMonkey]

Hmm I have a both (5D2 and 100-400) and I'm not seeing excessive dust I have to say.

I would also love a 70-200 2.8 IS, but really can't justify the cost, not much chance of the mk1's being that cheap either :(

[HoppyUK]

If you are going to be shooting mostly in the 200-400 range, get the long one. If not, get the 70-200 and extender.

[cirks]

Having both (ie 70-200 2.8IS + 1.4 and a 100-400), even on a crop sensor like mine, if most of the shooting you're going to do is wildlife then I would go for the 100-400 - particuarly on the full frame.

You'll find you're using the longer length much more than the short and therefore you'd need to have the extender on most of the time anyway if using the 70-200.

The only slight advantage you'll get with the 70-200 combo is the aperture. However, with the high iso capability of the 5dMkII you won't be struggling for shutter speed even with the 100-400 (nor DOF at the wildlife distances)

[tarmac_chaser]

I found a 70-200 plus 1.4x on a crop body at the zoo was sometimes still lacking, so I would've thought something longer would suit you better with full frame