Performance difference between 2gb card and 4gb

Solution
The GTX 960 4GB models are a waste on 90% of titles. The card simply doesn't benefit from the additional 2GB because the GPU on the 960 can't take advantage of it except in a handful of scenarios. I'd get the best 2GB card you can afford that doesn't cost more than any of the 4GB cards, or a 4GB card if you can get one for a similar price.

https://www.youtube.com/watch?v=iX_mW36BDKs


If you want to go with a 4GB card, I wouldn't spend any more than this:

PCPartPicker part list / Price breakdown by merchant

Video Card: Gigabyte GeForce GTX 960 4GB Video Card ($199.99 @ Amazon)
Total: $199.99
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2016-03-23...
The GTX 960 4GB models are a waste on 90% of titles. The card simply doesn't benefit from the additional 2GB because the GPU on the 960 can't take advantage of it except in a handful of scenarios. I'd get the best 2GB card you can afford that doesn't cost more than any of the 4GB cards, or a 4GB card if you can get one for a similar price.

https://www.youtube.com/watch?v=iX_mW36BDKs


If you want to go with a 4GB card, I wouldn't spend any more than this:

PCPartPicker part list / Price breakdown by merchant

Video Card: Gigabyte GeForce GTX 960 4GB Video Card ($199.99 @ Amazon)
Total: $199.99
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2016-03-23 02:18 EDT-0400



And really, this probably does just as well the majority of the time:

PCPartPicker part list / Price breakdown by merchant

Video Card: EVGA GeForce GTX 960 2GB SuperSC ACX 2.0+ Video Card ($189.99 @ Amazon)
Total: $189.99
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2016-03-23 02:19 EDT-0400
 
Solution
The main reasons why graphics cards come with more memory.
Relate to how powerful the model of the Gpu is on the card.

This allows you to not only display higher screen resolutions providing you have a monitor to display the resolutions.
But also the higher the resolution the more memory of the card is required to display the higher resolution.

Also it means you can crank the graphics quality of games up and the amount or FX the card can produce.

When you set a graphics card display resolution higher. and in game graphics and effects it requires more memory of the graphics card. as higher resolution texture require more memory space.

It can also help with in game loading where the actual textures are stored on the graphics cards memory for faster access. If the card has less memory on board from time to time you can experience a slight glitch or lag.
Because the card has to call textures for example from system memory to the texture memory of the graphics card.

Experienced as a slight split second lag while new textures are loaded for in game texture mapping.

But for system with a 1080p resolution most cards perform very well even with 2Gb of card memory over a 4gb enabled model.