I think 2 a week (evenly spaced), is good for beginners, but as you progress in your weight training, to avoid plateaus and get better results, moving to three is a better idea. And to keep making progress and giving your muscles more work, then moving to split routines.
It also somewhat depends on your goals and your genetics. Two days a week is good for maintenance, and some people can actually make gains with it (doing a heavy routine).