If we're talking sport BJJ, then I very much prefer side control. Don't get me wrong, I've got a decent mount game, but there's just so many more options from side control.
I like to set things up, then switch to modified scarf or N/S to finish. When you factor in the various side controls (scarf, mod scarf, cradles, 100 kilo's, twister side), there's just a lot more submission options.
It's also a lot easier to hold a guy down in side control. It's a lot easier to get reversed from mount when going for subs. Escaping mount, for both noobs and experienced guys, is almost always easier than escaping a good, tight side control.