It's really a toss up. Tanks are easier to heat, but tubs are easier to maintain humidity.
Tubs also require you to use a thermostat to control the heat source (a under tank heater) A thermostat is going to run you at least $30, but a good one is around $100.
Cheap Thermostat: http://www.amazon.com/Hydrofarm-MTPR.../dp/B000NZZG3S
Mid-Range Thermostat: http://www.reptilebasics.com/thermos...stat-prewired/
High Quality Thermostat: http://www.spyderrobotics.com/home/products.html
A tub setup is simple, all you need is 1 or 2 hides, a water dish, some form of substrate (paper towels/newspaper/aspen/eco-earth/etc. The one requirement is that you keep the substrate layer thin, 1/2" thick or less), a Under Tank Heater (UTH), a thermostat, and a probed thermometer (see below)
I recommend you get this thermometer regardless which cage style you go with.
You can get these at Walmart for $12. They measure 2 temperatures and humidity.
There are some simple/cheap ways to maintain humidity in a tank. You can:
1. Switch substrates to something that holds moisture in better
2. Cover 70%-80% of the top of the tank with aluminum foil
3. Get a bigger water dish
4. Mist daily