I've been using the terms "Optimists" and "Realists". The unfortunate problem is that there are actually three groups, the optimists, realists, and pessimists, but the pessimists have decided to clump themselves in with the realists, so it can get confusing at times.
The optimists and pessimists generally never agree, and both sides will agree with the realists from time to time. It may sound like there are conflicts, but for the most part, it just keeps things more interesting.