I think it basically goes like this: If you get one that works, ABIT KT7-RAID is great -- it has plenty of features, arguably better jumperless system (SoftMenuIII), more slots (1 more PCI and 1 more ISA), PLUS you get built in RAID...
except... they are notorious for having a noticably higher percentage of factory-defective boards. It's not a huge deal, you can either get your dealer to test it (if you buy locally or have yout computer assembled by a pro), or you can exchange it yourself... trick is knowing when the problem is the motherboard.
ASUS A7V is still an excellent board, although it doesn't offer RAID or any ISA slots. It does offer AGP Pro instead of regular AGP of ABIT (which I'm not sure any card uses anyhoo... so its a moot point), but they are arguably more reliable out of the box.
So basically, you can't go wrong
I was making up my mind between the two when I decided to buy 2 30GB drives and put them in RAID 0 -- this made ABIT prime choice for me personally. If you don't care for RAID now or ever in the future, it's 50-50
Hope this helps somewhat
Good luck,