5D classic or 7D for wedding?

Okay so far I have a 5DII, 70-200 2.8 IS and 24.70 2.8. I am deciding whether I should go for the 7D or 5D classic for the 2nd body. I figured these are the benefits for each camera:

5D classic: Image quality is still top notch compared to other cropped sensor cameras. Some even claim its better than 7D in term of IQ. More consistent shots with my main camera because of the FF .
7D: better AF than both the 5D and 5DII which means less missed shots. Possible better ISO performance than the 5D classic in the 800 range.

Which one is better. If you do wedding with the 5D classic, what do you think of the pictures at ISO 800?

Please state your reasons for recommendation and what type of work you do

Oh and the 2nd camera body is not a backup. I will attach one of the lenses to it and use it in with the main camera

First let me say I don't shoot weddings. So, this is just an opinion. Going with a top of the line crop will give you another focal length perspective without buying new lenses. That is a plus. The down side is you now have different bodies so switching from one body to another won't be as seamless? I don't think a wedding typically requires alot of "reach" focal length wise which is why the pro's tend to use the 70-200mm alot so I wonder if you actually "need" the extra reach of a crop factor? If I was a pro and needed a backup I would want the exact same bodies but just different focal lengths attached. So I guess what I want is not really a "backup" but a second working body.

I'd take fullframe any day. 24-70 and 70-200 on FF are the bread and butter focal ranges for wedding photography. I've shot only a few, and only one with a fullframe. I loved FF then, and got myself a used 5D thereafter.

I've thought about this a lot, and have decided to go with another 5d2 when I get the money together.

Red Tie Photography wrote in post #10185701
I've thought about this a lot, and have decided to go with another 5d2 when I get the money together.

good decision. for wedding work you cant beat FF.

I had the same issue. Only I started with the 5D classic and was looking at getting a 5D mark 2. I shoot mainly weddings. My biggest bone of contention with the 5D was the AF. With prices of used 1D mark 3's almost the same as a 5D2; I joined the 1D mark 3 club. ISO performance is better than the 7D (at least according to DP Review). The crop factor isn't that bad either. I have been pretty pleased so far. And the autofocus is ligtning fast.

If what you have is the 24-70 and 70-200, I'd say get another FF camera. For a wedding, I'd rather sacrifice reach for being able to get 24-35mm in there. I don't know how often you'd need it, but you could always still rent a 5D, cheaper than renting a 5D2, but still pretty kick ass.

I say go with the 7D, you already have a FF so to get the most out of a second body getting a 1.6x crop will allow you to reach further with lenses you already have.