Onto the Tyan board, Tyan does not usually cater to the consumer crowd, they’re mostly business oriented (CAD draftsmen, OEMs, etc.). That said, most of the audience would know the specifications of the E7205 chipset that is powering that board.
The E7205 is replacing the i850E boards with dual channel DDR instead of dual channel RDRAM, both have HT support (as do all Intel chipsets which support the 533 MHz FSB), and has an onboard 10/100/1000 (Gigabit over Copper or GoC) ethernet. And, if you read up on the specs of the chipset, the specific ethernet chipset is one of a few made by Intel that are designed to go not over the PCI bus but rather directly into a specially designed northbridge IHA port (similar to the one that the ICH4 plugs into).
In addition, the board can support full bandwith from both ATA/100 channels and the PCI bus and the Gigabit Ethernet connection with no contention … that is, there is more than enough bandwith available for all of the above.
Since it’s designed to be the UP workstation chipset for Pentium 4 processors (replacing the i850E, as I said before), it supports higher total system bandwith than any other Pentium 4 or Athlon solution, with the exception of boards such as this one based on ServerWorks chipsets. As long as you use the onboard ATA/100 over an add-in controller card and use the built-in gigabit ethernet, you will not suffer any bus contention or performance degredation whatsoever.
Tyan caters to the crowd that demand stability over performance, and still perform near the top of the pack in performance. This puts them in a class with themselves, SuperMicro and Intel mostly. Little to no OCing features. Then again, as I mentioned before there is little headroom in either the Athlon or P4 processors currently, so it’s not of major concern.
The Asus board is jam-packed with features: SATA/150, ATA/100, IEEE1394, Gigabit LAN, etc. This is all well and good, unfortunately the SATA/150, IEEE1394 and Gigabit LAN share bandwith with each other and everything else on the 133 Mb/s PCI bus. This will lead to a large performance bottleneck when you add a good sound card and whatever else you throw into it.
The Tyan board is stripped of all but the Gigabit LAN and ATA/100, and will probably cost around the same amount of money, but because the Gigabit LAN is on its own bus, will likely offer higher performance. In addition, the Tyan will offer more stability and compatibility. To date, the Tyan boards are the only ones that don’t have issues no matter what PCI slot you thorw something in with their Socket 370 Via AP133A/T chipsets. They do, indeed, know how to make a board that just plain works every time you push the power button.
Another thing to consider is that Tyan offers a Radeon 9700 Pro card (this one here) of their own making, which would make troubleshooting much easier (they validate their cards for their boards so you know it will work, period), and reduces the number of vendors in your system (usually a good thing). Asus only offers up to a GF4 Ti 4600.