If you like Bach horns, check out the Bach 16 series. That's what I use, personally, and I love it. King 3Bs and 2Bs are industry standards, and any relative horn from Yamaha, Getzen, Conn, or the other major horn manufacturers would be others to check out.
In the end, play as many horns as you can, even multiple different horns of the same model. The more you can manage to try, the greater chances of finding that gem of a horn that works for you specifically.
Spend some serious time on each horn, as much time as you can, in order to get a real feel of what it feels like for you. If you can, bring someone along that knows your sound to give you another set of ears for even more info.
It doesnt matter what horn you have. Jazz isn't determined by horn, its by knowing how to play it. A lot of new guys are starting to use bigger horns as it is, so getting a peashooter is almost proved obsolete. I play a Bach 42 and King 2b Libterty. The thing is though is I can play whatever on each. I use the King if I need to cut through a lot of sound like playing with a funk band. However, as far as Jazz Bands go, it might be best to stick with something that will blend more. If you want to hear a largebore Jazz Trombone player. Listen to Robin Eubanks and be prepared to !***! yourself. Sorry for the crass language.