Graphics Card Memory

Solution
If you run games on ultra settings then yes 4 gigs if not 2 should be fine also depends on the resolution 1k/1.1.2.../3k/4k all have a huge impact on memory.
Advantage of having more than 2gb of vram is if your gaming higher than 1080p. The thing with with r9 270x is once you go higher than 1080p quality suffers so getting this card for gaming higher than full hd is not wise