The Asus A7M266D, MSI K7D, and Tyan Tiger MPX are quite similar in performance.
The Tyan Thunder K7X/Pro is the most stable and most powerful; however, this board is extremely expensive when compared to the other 3.
Thunder K7X Pro S2469UGN (gigabit ethernet/ scsi) lowest price at 451 shipped
Thunder K7X Pro S2469GN (gigabit ethernet) lowest price at 360 shipped
Thunder K7X S2468UGN (scsi, 2x3Com 10/100) lowest price at 420 shipped
Thunder K7X S2468GN (2x3Com 10/100) lowest price at 333 shipped
General
specs are here.
Thunder Tiger MPX S2466-4M lowest at 205 shipped
Specs
Asus A7M266D lowest at 164
Specs
MSI K7D Master lowest at 207
Specs
If he is just considering the A7M266D, K7D Master, and the Tiger MPX, I would say go with the Asus. If he has a lot of cash, he should pick the Thunder K7X that best suits his needs.