The A70 also has DiGiC processing, but I the reason I chose the A70 is for it's superior movie move(it can do 640x480, the S400 is limited to 320x240). Not really a BIG deal, but I do appreciate the fact that I can capture "quality" stupid moments on film when the occasion arrives =)
I didn't realize that the AiAF was different though =(
I think the A70 actually has slightly better picture quality in terms of optics since the S400's optics are compromised by having to fit so closely so you get more chromatic abberations and more darkening in the corners.
Personally I went with the A70 because it was a good deal(like $250 with 128MB CF card and a reader even though I already owned a reader it's nice since I have two PCs so now I can load to both of em easily).
But I did feel pangs of jealousy when someone else had an S400 bought for them...bah!
Forget it, someone get me $7000 so I can buy the 1Ds and never be jealous of 99.9999% of camera
And damn you people, this thread has started up my brain gears cranking again and now my stupid capitalistic competition buying urge is starting up again...as if a 3.2MP 3X optical zoom camera with DIGIC and 5 point AIAF isn't good enough...even though it technically has better lens quality if you look at the pics...plus that better movie mode...
I guess the only way to settle this is to buy the G3. DAMN YOU ALL!