The other is a KT133A chipset and uses PC100/133 memory.
I think DDR is not mature enough yet to justify buying, personally. PC133 RAM is cheap as anything out there and it's been proven that the KT133A chipset comes very, very close to DDR performance at a lesser price. If you're asking me what I would buy at this point - I'd still say the Abit and stick with PC133 memory. I think DDR is the future, but to me it's not going to be a viable platform until the Via KT266 chipset comes out and sets the performance par for all other DDR chipsets.
I have built and sold/used Abit boards myself, and had good results. But in the recent past, there is soooo many guys that are having problems with the K7T133a (I believe a lot of these are SB Live! and poor power supplies) But, anyway...except for the SB Live!...when the guys RMA the Abit, and get the Iwill KK266-R (if they want Raid) problems vanish.