The Won titaniums are what I use, and they work great. The nice thing about a titanium heater is that the tube is grounded so you get a grounding probe as a bonus.
On a 100 gallon tank, 350 watts would probably be best. I'd use two 250 watt heaters to do the job. This way if one sticks on, the thermal runaway will be slower so you can catch it in time, and if one fails, the other can still keep the tank warm. Set one thermostat a couple degrees behind the other and it gives you a nice two stage heating effect.