The T-stick and the J-stick, in addition to having different features, have a radically different feel. The feature set is better on the T-stick, but I think most people would prefer the "feel" of the J-stick. It has a looser feel that is closer to the feel of old school 4-way games. If you aren't interested in the switching mechanism of the T-stick, then the J-stick is probably a better choice anyway.
-Jeff "etumor"