I would be interested to know how many people commenting on this thread have actually used the A77 and its apparently awful EVF.
I love Canon, always have. I started with a 350D and moved to a 50D but with the imminent arrival of my first child I felt an upgrade was justified. The obvious choice was the 7D - my dad has one and I like it a lot.
But, it is quite an old camera now - particularly the sensor technology and there were certain features of the A77 that I thought I would make full use of - things like focus peeking and on paper the EVF had certain advantages as well as disadvantages. For example, an overlay of the histogram and the fact the the DoF preview button can be set to show exactly what the actual shot will look like, thus somewhat mitigating the low light issues.
It wasn't an easy decision, I had a few lenses and as I say I am (or at least was) a Canon shooter but I took the decision to move to the A77.
I can't say whether I would be happy or not with a 7D as I didn't go that route but having used my dad's I don't think I would have minded having it.
What I can tell you is that I am delighted with my A77 - it really is a lovely lovely tool to use. I get far more keepers with my A77 than I ever got with my 50D and I enjoy using it far more. Now I am used to the layout of the buttons etc the handling is first class.
To say the EVF doesn't display in real time is misleading. It does except in high speed shooting mode. In normal lighting conditions, when concentrating on the composition of the shot, the subject etc I forget I'm looking at an EVF.
In low light, yes it is noticeable but not so as to be off-putting and bear in mind you are seeing what the sensor sees and what it will capture. If it is too dark to see - unless you are using flash - the shot will be underexposed.
To the OP - to be fair I don't do much BIF or sports where high FPS matters so can't comment on high much of an issue the fact that you see slightly delayed shots, not a real time view at 8 or 12 FPS but remember on the 7D the mirror keeps moving up so you lose sight of what you are shooting also. Swings and roundabouts.
I would seriously suggest trying both systems - do try the 'kit' 16-50mm with the A77 - it is a special lens. Play with the EVF, play with the 7D and all its features. Heft them in your hand see which feels good and make your decision from there.
I don't think you'll be disappointed with either and certainly don't be put off the A77 by some of the comments on here about the EVF from people who, if they have seen it at all, have given it a cursary glance.
Apologies for the length of this reply and please try not to label me a Sony fanboi as that I am not - I am just trying to offer (possibly some what in vain) a balanced opinion of someone who has used both cameras. If I could afford a 5D mk III to complement my A77 I'd go out and buy one tomorrow and I love my S90 and would kill for a G1X and would take a S100 over the RX100
Cheers
Danny B
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Shoot lots...
http://www.dannybowerphotography.co.uk