The K7ADA uses the first ALi Magik 1 chipset, which, when equipped with DDR, performs only as well as KT133A with SDram. Not to mention that many people feel bad about products from ALi. I recall some to have problems with Ali southbridges and Radeon cards. I've never used an ALi chipset board, but from what I've heard, I wouldn't get any ALi board.
The Shuttle AK31 3.1, on the other hand, has the high performing KT266A (it outperforms ALi Magik 1 by about 25%). The shuttle is the cheapest KT266A board, but it does not scrimp on anything at all: 6 PCI, 4 dimm, full overclocking bios, etc.
If you have more $, you can get the EPoX 8KHA+ Via KT266A board for $100; the Asus and Abit boards are too expensive.