I respectfully disagree with mmadmikes1. I use a "brew bucket" which will hold about 7G to the rim as a primary for my wine kits and I've never had any problem with it. If you were buying something either way I'd say get the 8G but if you already have a 7G it should work just fine and you can use the money you saved to buy more bottles or some fancy labels or something.
Also- FWIW- My wife and I just bottled that kit not too long ago. It makes a pretty decent finished product. A little sweet for my taste but I'm not a big wine cooler drinker. My wife (who likes wine coolers) loves it.
There are good ships, and wood ships, and ships that sail the seas, but the best ships are friendships and may they always be.