GTX 780ti or GTX970 at same price

At the moment I can get gigabyte 780ti or asus direct cu II oc 970, both second hand at the same price (about 300). Which is the better card. I am still new to blender so i am not certain what to take.
I have read that 780ti is a bit mower powerful but has a much higher tdp of 250W and less Vram (3gb). Is the higher the 1gb extra VRAM a big deal alongside the lower power requirement.

It really depends on the kind of things you want to render. Huge amount of polys-> need lot of Vram. Huge (amount of) textures? need lot of Vram. What graphics card do you have at the moment? To decide on my new Graphics card, I opened the most graphics-intensive scene I had, let it render, and then used GPU-Z to see how much VRam I use. Then I multiplied that by two (assuming that in the future my projects will double in complexity), and chose for a 980 with 4GB.