I like spiked chain for tripping, especially the Living Spiked Chain, +2 trip checks. Although I play 3.5 haven't played PF yet. Playing a unarmored swordsage with 2 lvls monk dip (DM ruled that SS wis to AC and monk wis to AC stack when not wearing armor).

Feats: Exotic Weapons, Combat Reflexes, Improved Trip, have some decent strength, and equipment for tripping, overall my trip check is 14 and 18 if I use a tripping maneuver from sword sage (about to turn lvl 12). Although at 12 I get to quicken truestrike 3/day since my race has truestrike and I took Magic in the blood for 3/day, can't wait to be quickening it.

I didn't like the whip mostly because of the in melee negatives it has, although no idea if you can get rid of those and make whips better, pretty new to D&D in general.