Amount of VRAM makes not much difference in mobile GPUs. 1GB is more than enough VRAM.
Its the bus width(64-bit,128 bit, 256 bit), RAM type(DDR3, GDDR5) and the shader count that matters.(But dont compare that by absolute nos. Nvidia and ATI/AMD counts them different as they have different architecture)
— Updated Post - Automerged —
More VRAM is just marketing tactic and sadly people who dont know much about GPU’s (common Joe) falls for it.
Heck even Nvida’s Desktop flagship GTX580 has only 1.5GB VRAM!