Re: Ki-Aikido or Taiji - effectiveness in developing Qi?
I think you should consider what sort of training you are up for. Tai Chi should really be done with chi gung and is possibly more complex than ki-aikido.
Any aikido means a lot of rolling around, how are your knees? Ar you up for learning to roll, can you roll already.
Add to this what are the individual teachers/students like, class times, ect.
We found that most students take up a particular form because it fit in best with there work schedule.
Doing something is better than doing nothing, and both are good.