Quirrell vs. Snape
If Quirrell and Snape fought in book one who would win? Both are powerful wizards. Quirrell only pretends to be frightened by alot of things so people don';t suspect him to be evil. But I think Quirrell really was afraid of Snape. If he really was stronger than Snape wouldn't he have just finished Snape off in the Forbidden Forest? Unless he thought there was to much at risk for him to chance a fight, for he might lose. But at the Quidditch match Quirrell nearly had Harry off his broom, even with Snape trying to keep Harry on the broom, which suggests that Quirrell is stronger than Snape. Who do you think would win if they fought?
For now I'll say Quirrell and he only didn't kill Snape in the Forest because he wasn't entirely sure he could defeat Snape.