My experience is that I can cast farther and with greater precision with a baitcaster. That being said, you have to practice... A LOT. There is a tensioner for the gears. You have to balance the tension for your personal style to avoid backlash, but still get a good distance. Backlash is bad, very bad. It creates the worst tangle you've ever seen. A bad one and you just have to cut the line out and respool your entire reel. Most times you won't be able to just pick up your friends baitcaster and cast it without re-adjusting the tensioner (at which point they'll probably use you for cutbait).
However, it's well worth the practice. When I regularly fished for bass I could drop a lure into a 2" square underneath a low hanging bush from 40' away. You just won't get that kind of performance from a spinning reel.
From a technical standpoint, baitcasters generate less drag and friction on the line during the cast.