Do I have to listen to my apartment manager when they recommend a electricity provider?

I'll be living in the Brazoria county area and my apartment manager says that I must go with TXU energy as they have a contract with them and their rates are around 17-25 cents per kWh depending on the plan.

I use approximately 250 kWh in normal months and around 450 kWh in peak months of summer and winter when my AC and heater are working hard. Does anyone here have experience with TXU energy? It's a 12 month contract with a $150 deposit so I don't want to mess it up.