You probably should decide which tire will best suite your needs before deciding on a wheel. You're going to be able to find a LOT more ATV tires (and more aggressive tread) in a 14", but you'll have a better selection of larger truck tires (30", 31" and 32") with a 15" wheel.
Where are you located and what type of terrain do you ride?
Beadlocks are debatable. Like most things, there are pros and cons, and "most" people will never benefit from having them. I have them as peace of mind because I have had flats a couple of times and didn't notice it until it was too late and the tire had already come off the bead. But they also have a tendency to retain mud and cause balance issues, and they tend to weigh a little more than standard wheels.