As a die hard game, I would pick the GTS. Reasons are the following:
1)Geforce 2 GTS much faster than the Radeon
2)Drivers - With OpenGL games, I have not experienced any problems with my ATI Radeon. But when you get to Direct 3D games, I have experienced many problems.
3)DX8. I am experiencing problems with a DX8 app with ATI DX8 drivers. I am not sure whether their newer drivers will be fully DX8 compatible. Of course, NVIDIA hasn't released their DX8 drivers yet but I am sure they will be much better than ATI's.
4)HyperZ - As a gamer, I play a lot of D3D games. Unfortunately, ATI couldn't come up with a stable drivers to support HyperZ in Direct 3D so they disabled it. This creates alot of choppy gameplay under intense scenes, especially on Unreal Tournament, a problem I did not experience with my Geforce 2 GTS. If you enabled it in the registry, it improves performance but also causes a lot of image corruption in D3D games.
5)Overclocking - If you are an overclocker, then you will want the Geforce 2 GTS. With the ATI's Radeon, once you get to around 193MHz, it runs out of gas. No matter how much higher you overlock it, it won't make hardly any difference. There is a big difference between 166 and 183 but barely any difference between 183 and 200MHz. The Geforce 2 GTS I have been able to overclock to 250MHz core/400MHz memory and the performance keeps on increasing significantly. You get much more bang from overclocking a Geforce 2 GTS than you do ATI Radeon.
6)Customer Support - I don't know if I should be posting this since I do not have any experience with Creative Labs or Asus as far as Customer Support is invloved but I have had problems with ATI drivers and ATI's customer support is horrible. If you are having problems with ATI's card, don't expect good customer support from ATI.
I can go on with other reasons but the above reasons are just things that would interest die hard gamers.