I run the Sirio Big Bore. It is a nice all around pipe. It's diameter is nice to give you some extra torque at the low RPM range. Plus it has some length on it which helps out with your top speed. If I had the chance to buy another pipe, I would purchase another Big Bore.
Match that pipe up with a Motor Saver air filter & you will noticably see a difference in performance.
Of course, make sure you re-tune your motor to accomodate for the new pipe (whatever you choose).
I think the THS pipe will only give you better performance at high RPM (or top speed). But I may be wrong, hopefully others can comment on the THS or AE for you.
Later....