The 2-year program has its advantages as well as disadvantages.

While you get to study the subjects in detail and get a chance of working part-time (in some cases), there is also the fact that the course fees is usually more and the living expenses are incurred for 2 years rather than 1. You also have to take a break from work for 2 years instead of 1, and hence you forego your earning potential for 2 years instead of 1. Depends on what you prefer!

Between Birmingham and Aston, the latter is triple accredited. Also, both are located in Birmingham and feature in the FT list, although Birmingham is the more traditional of the two, and in my opinion, the more reputed as well.