in my point of view its 100% the same result! no matter its a requirement for an openGL version or not.
even if there is no s3tc the game engine can not deliver a competitive results because of the limitation of the bandwidth of the vram.
on the vram size you can just buy the bigger card maybe a 4gb vram card or more but on the speed side you can not have more GB/s out of your ram interface.
bigger size in vram means it need more GB/s bandwidth for the same result!
this kind of "opensource" game engine will just lost all competitive benchmarks and competitive optical customer reviews.