Calling down a bluff with ace-high? +EV?

This situation seems to happen to me a lot, both online and in my home game. I'll get a read on one of my opponents, especially one particular guy at my home game, and call down a hand with say, ace-high or bottom pair. Now then, is it better to come over the top on the river and take it or just call him down? I usually mix it up, but it seems like it's +EV to just call him down for two reasons: It says "You can't push me around," and a good percent of the time my opponent will tilt at least a little bit. So which do you think is +EV and why?