Main use of the different bows:

Longbows: good for luring, appreciable in some places where you should stay far from the ennemy (I'd rather use a longbow in a B/P tomb team for example).

Flatbows: they have the same range than longbow, but they send arrows 10,000 feet in the sky and take ages to reach the target. They have a very poor accuracy since a foe moving will dodge the arrows. That's the only bow I never use.

Composite/recurve bows (same kind): they have a medium range but a very good accuracy. They should be used for interrupting, and if you dont have a hornbow, it should even be the default bow on most of the maps (ie: on all the maps were you don't need to stay far away from your opponents to have a chance to stay alive - ie: if you're not in the tombs or maybe in sf).

Hornbows: better accuracy that flatbows, but still it's not that great; medium range as well. However they have 10% armor penetration, and are recommanded if you're a damage dealer, but you may want to use a recurve bow instead - that's a matter of style.

Shortbows: good accuracy, they strike fast (2 secs to shoot an arrow), but they have a short range. Use those when ennemies come near and when you're ok hp wise (otherwise step back behind the tanks...). Most of the rangers don't bother with them as most of them don't switch their bows, however I highly recommand those.

- EDIT for typo(s) - Sry about the bold part, Tank. Side note: thanks, Divine Ambassador: I still remember our run in the Deep - yeah I may be injust with flatbows... that's just a personal grief against Drago's flatbowers :P