i'm getting one this week and i wanna know if it's worth it. there is probably already a thread for this but i refuse to find it.

also does it matter which one that you get?

Ya, what D3v said pretty  much covers it.  Here are some of my thoughts on it.  When i first bought the TE stick, i was pretty much instantly better with transitions from one button to the next, and combos with the pokes, jabs, etc.  I also felt like the moves had a more positive input.  One of my gripes with the D-pad, was in an intense match, i'd find i could end up holding it soo firmly in block, that the whole cross ended up pressed at one time, causing me to come out of block.  The other issue i had, were my hands.  While the D-pad is the most natural for me, my hands would cramp up after long sessions, and i'd miss moves frequently.  I also had a hard time getting to the combos, jabs, pokes, because of the L and R button locations.  However, it did take some time to become "as good" with some of the motions on the stick, as i was on the d-pad.  I began using the stick as somewhat of a handicap, and novelty when fighting my son and his friends.  Or anyone on my friend list, that just didnt play as much as me.  Unfortunately for them, i ended up very good on the stick, and its now my preference. 

Like d3v, it depends on your personal preference. Just because many of the top ranked players use a stick, it doesn't mean you can't pose as a match while using a pad.

I think it's boosted my execution. It did take a few days to get used to though, but once you get back to where you were, there's nowhere to go but up.

I just got a TE stick the beginning of last month and I'd say it helped me understand how to link and do combos and stuff a little better. I switch back and forth between my stick and pad (PS3) and I've gotten much better with the pad because of the stick. I'm a Gen player, so there are some things that just can't be done on a pad (e.g. MK Hands), but what I lack on the controller is made up with my ability to move around. I'm still working on my mobility on the stick.

I like playing with both. I don't play with the stick online all the time though. It's harder for me to adjust to lag on the stick than on the pad. Either way is good for me though.