Radiant heat is especially nice in a bathroom, it's very nice to step on warm tiles with your bare feet. It's one of my favorite things about my bathroom.

You mean for spot heating, for example while taking a shower? Maybe neither of those; a kickspace heater or heater in the exhaust fan might work better. If you mean a heater to heat the room in winter, you'd best discuss with your HVAC contractor. I'd prefer radiant heat under the tile but if the thermostat seldom goes on because the bath is an interior room, you'd have cold to the touch floors anyway.