Shotokan is best for standing in front of a mirror practicing stances and defensive techniques that will never work in combat or competition, as well as doing ancient Okinawan Folk Dances known as "kata" where you have another outlet for practicing techniques that won't work outside the dojo. (I have a BB in Shotokan, lucky me...) If you are looking for old school traditional Karate it is A+, for fighting it is C- (see Lyoto Machida for a very notable exception to this, though)
Kenpo is like Shotokan except with a pseudo chinese or (allegedly) Hawaiian influence and black Gi with more corny patches. There are several different flavors. The tend to spar more than Shotokan which is better for fighting. They get in lots of pissing contests about which school/lineage is the more "authentic". They teach goofy "secret" pressure point shit that everyone else in the world already knows about and doesn't work well anyway. They seem to think that "flurries" (also known as combinations everywhere else in the combat world) are some kind of original technique, but at least they do teach combos. The footwork is marginally more useful than TMAs that don't spar much. For TMA I give it about a B. For fighting about a C+.
Kyokushin was the original bare knuckle full contact style started by Mas Oyama. It has also split into several styles. Back in the day it was the shizzle. After waaaaaay too many hand and facial injuries the main style of Kyokushin banned closed fist punches to the head in competition, resulting in it becoming sort of like half-assed Tae Kwon Do. If you can find a Kyokushin Dojo that still works punches to the head it is good stuff. Some of the offshoots also incorporate Judo (Kudo) and have their own system of MMA competition. Hard to find in the US though. For TMA I give it a B+ and fighting a solid B (assuming they are teaching sufficient hand techniques and defense).
If you want good standup and don't care about oriental mysticism, role playing, and wearing costumes try kickboxing or muay thai. Thats just my two cents...