what are you planning to run in it? The Tul2 is just an upgrade of the Cusl2. The Tusl2 supports the new Tualatin P3. I never heard of the 3rd board you mentioned. I highly recommend the ABIT bx 133 R board. It runs the BX chipset, which is faster then the 815, and as stable as they come. You also get the 4 extra IDE devices even if you do not plan on using the Raid. I have this board and it is by far the best board I have had.
Pentium 3 1000 @ 1100 ( windows 2000 server), Abit bx-133, 256 Mb Mushkin Rev.3 cas 2-2-2, ATI Radeon
AMD Thunderbird 1.4 @ 1.63 (24/7) IWILL KK266R , Corsairs pc 150 cl2, Leadtek GeForce 3