How do they compare between graphics cards and classify them?

[yazooda]

Guys, I really wonder about that, for example:
GeForce GTX 690 1 GB is much better than GT 210 3 GB ! Really why? What is the thing they rely classifying graphics cards (GPUs)

Sorry for weak English accent

 

[Beezy]

a combination of factors, amount of stream processors, shaders, cuda cores, RAM amount and bandwidth. 3GB on the GT 210 is probably GDDR3, while the GTX 690 is GDDR5. GDDR5 is twice as fast as GDDR3 so its like 1GB is actually like 2.