If done well, you can use a heatlamp without sacrificing your humidity. I use both a UTH and a heatlamp. The tank I had (didnt want to buy a new one) is too tall for the UTH to keep the ambient air temp up. I got a lamp hood for the top, closed a good portion of the rest of the screen top off with aluminum foil, and humidity stays around 60% the entire time (in a typically air conditioned room). I never really see any fluctuation in it, +/- 2%. I will say it can make for a pain when trying to get your ball out! I think if you go with the heat lamp you just need to make sure that you do everything right to make sure the stats are correct. (Either way, I'd go with a UTH as well with a thermostat, takes a lot of the stress away worrying if your enclosure is suitable).