If you are using a 1920 x 1080 resolution then extra 1GB VRAM will not make much difference, and 7790 is a better card than 7770. So I would go for 7790.
If you are using a 1920 x 1080 resolution then extra 1GB VRAM will not make much difference, and 7790 is a better card than 7770. So I would go for 7790.