As to which chipset is best, that depends on your intended use. If gaming is your main interest, go with KT266A. Whereas if your main use will be disk-intensive apps, I would go with ALi MAGiK 1 (C1). But IMHO, the best board with the ALi chipset is the Iwill XP333, not the Asus.
<b>God bless the <font color=red>U</font color=red><font color=white>S</font color=white><font color=blue>A</font color=blue></b>
right, the Iwill XP333 (in its latest rev) is a better board than A7A266-E simply because it supports better overclocking and officially the DDR333 although by overclocking the chipset! Asus board sint so oc friendly, but lives upto the Asus tradition of rockstable boards, I have one A7A266.
both are good boards, and the ALiMagik1 (1647C) does catch up with the KT266A for once. so if your main concern is stability and compatibility, go for Magik, if you need that slight sped avantage (and the onboard RAID that comes with the A7V266-E) go for V266-E.
nothing much separates the two, compete well on all benches.
<font color=red>Nothing is fool-proof. Fools are Ingenious!</font color=red>