So, I'm asking that, since I've got a GTX650Ti 1 GB graphics, and it takes 5 minutes to render a simple 1 minute video with minimum effects. Is it normal? I've tried it both with Sony Vegas and Adobe Premiere Will the 2 GB version of GTX650Ti increase performance?
Not likely. Graphics card memory is more about loading information on to the card for textures and such for rendering. It isn't really a key component of pushing information through the GPU itself. When using a GPU for rendering, we are interested in the high level of parallel performance that a GPU can reach for relatively simple calculations. The rate at which information can move in and out of the card as well as the rate at which the GPU can process matters, the memory on the GPU is not generally going to be a bottleneck.