Directly related to your question:
http://forums.taleworlds.com/index.php/topic,168199.msg4082648.html#msg4082648
http://forums.taleworlds.com/index.php/topic,195750.msg4690772.html#msg4690772
http://forums.taleworlds.com/index.php/topic,110164.msg2676761.html#msg2676761
http://forums.taleworlds.com/index.php/topic,111379.msg2696950.html#msg2696950
http://forums.taleworlds.com/index.php/topic,154049.msg3699133.html#msg3699133
http://forums.taleworlds.com/index.php/topic,158498.msg3813557.html#msg3813557
http://forums.taleworlds.com/index.php/topic,120933.msg2921285.html#msg2921285
Vonskyme's Powerdraw guide
Related but through discussion of troops and related character builds:
http://forums.taleworlds.com/index.php/topic,172928.msg4162923.html#msg4162923
http://forums.taleworlds.com/index.php/topic,188257.msg4507568.html#msg4507568
http://forums.taleworlds.com/index.php/topic,132355.msg3189972.html#msg3189972
http://forums.taleworlds.com/index.php/topic,130765.msg3151393.html#msg3151393
http://forums.taleworlds.com/index.php/topic,180576.msg4348305.html#msg4348305
http://forums.taleworlds.com/index.php/topic,178736.msg4299279.html#msg4299279
http://forums.taleworlds.com/index.php/topic,172449.0.html
My 2 cents: Bow. With high powerdraw you are more powerful than an xbow, faster, can use it on a horse, and ammo is more plentiful.