First of all: UT had more polygons than Q3A, especially in the charaters. The environments were also much larger, but with approximately the same level of detail. The reason UT looks "worse" is because it actually has higher sys req's that Q3 if you want it to look like it was intended to. Q3A has OpenGL mode, the 3dfx MiniGL mode(3dfx Glide itself is a subsystem of OpenGL, modified to work best with games and the Voodoo chipsets, much like an early DirectX. MiniGL is the actuall OpenGL driver for 3dfx cards, with OpenGL's calls rather than the card-specific Glide calls. It was added when OpenGL appeared as the standard API.) and Q3A supports software mode, you just have to go through hell and back to enable it.
And nVidia's T&L was made for OpenGL-based workstations, it was only added to personal computer cards later if I'm correct.