Moon_Rock :
Would minecraft shaders run better on Windows 8 or Ubuntu?
Technically it should be faster as Linux in general uses less resources than Windows. However It highly depends on what gpu drivers you have.
You'll have to use the repository drivers for your gpu or find them online for linux, and then see what fps you get.
If you don't have copy of Windows right now then I can't really help much more.
But i did get better fps in TF2 with my gtx 660 when using Ubuntu before.