My main bow for both PvP and PvM doesn't have mana leech, but I have meditation, lower mana cost and mana regeneration, so I only have mana trouble in the huge fights (Peerless/champs). I also don't have any stamina leech on my bow since divine fury not only restores my stamina, but increases my swing speed.
But if you don't have med, MR, and LMC, I would very heartily suggest using mana leech bows.
I typically use composite bows for armor ignores, but when there's another archer with a crossbow or heavy crossbow, I often switch to my own (the crossbows outdamage the composite fairly easily).
For small fights, a yumi can be priceless. With a mana leech yumi and a reptile/dragon slayer yumi, you can even solo the Oaks spawn (you come out far ahead on the arrows used by looting centaur), which is something I have failed to do on every other template.
So which bow you use is definitely a situational thing, and depends on your template, suit, tactics and what (or who) you're fighting.