If I am looking for a video card and I have already selected a specific chipset (for example, the NVIDIA GTX 770), is there really a large degree of difference between the companies who construct the physical cards?
I was thinking about brand x but brand y looks just good. Is it really all just marketing?
There are measurable differences between a 770 from brand A and brand B, however with so many brands and possible differences, the answer is very broad. Amount of memory, outputs, clock speeds, memory speeds, heating/cooling, noise, etc, all play a factor.
Your best bet is to find a website that reviews both the cards you are looking at. These websites will post their metrics on the cards and rank them by performance.
