32 bit video cards are probably even today the biggest selling type of card but anyone seeking real graphics performance should be looking instead at 64 or even 128 bit cards. Investing in a high end video card pays back in a matter of months rather than years as productivity increases. Of course there are other things that influence video speed. The amount and type of memory on a video card is a major factor as well as the way the memory is addressed. An application calls for a graphic to be drawn and the video card grabs as big a chunk of the image as it can, draws it and then goes back for another chunk of the image.
Complicated graphics can use quite a few chunks of data and take quite awhile to draw.
The more memory you have on your video card the larger the chunks that can be redrawn at a time. The faster your memory is the less time it takes to do that redrawing. There are two main types of video memory. VRAM is the fastest but rarely seen in video cards except in the very high end. If your wallet is fat enough to handle the load, insist on VRAM for your video card.