Karate, Kendo or Judo

[Boxy]

I guess this is a bit more of a question of what you're looking for, you say you're into contests so, that's something both judo and karate have in an abundense (kendo isn't lacking either but those two just stand out in that field).

So lets say we're down to those two ok?
now it boils down to the question of what you want to improve:
1) If you're looking to go into MMA or more street like self-defence+ major confidance boost striking is a must, not an option, just ask Gabriel Kitober; went into MMA as five times champion in BJJ but got his A$$ handed to him by a guy who just low-kicked him to the ground in the 9th IWC (though in his defense I will say that when he took the guy to the ground he nearly killed him), judo would improve your stand up grapling which should be desent if you're sick and tired of BJJ but karate has some of those elements as well (depending on style).
2) If you're looking to improve your grapling (and putting on a few pounds of mass) than look no further than Judo, it would imensly improve your stand-up grapling with its throws and it also has a few things you might have picked up in BJJ, so you won't be too much out of your element.
Also all of the Judokas I know are rather large and well built, so i'm guessing the two are connected.

in general if I had to grade these two arts it would go like so (scores are given out of ten):
karate
Stand up striking: 8.7
stand up grappling: 4 (some styles have good elements but others are completely lacking hense the score)
ground work: 2 (only ippon finishing blow if i remember right)

judo
stand up striking: 2
stand up grappling: 9
ground work: 6 (from expeirence sparring against two brown belts and one black belt in bJJ)

these are my own personal scores and they are I admit subjective to my opinion so feel free to state otherwise if you think so

[Munkymagic]

I've posted loads about Judo in the past...ive been doing it since i was a kid, not so much anymore though due to arthritis. It is a fantastic art, applicable to MMA and in my opinion is one of the best street defence tools going. it can be pressure tested at full speed as there are no lethal techniques and your standup and balance will become second to none...plus it will give you a more than half decent ground game. Depeding on what you want...it wont give you the tools of BJJ on the ground but the stand up is great if adapted for MMA. If you want it for self defence it will give you an edge over 95% of the mugs out there including some of the so called MMAists who train pure MMA (those who have never studied a pure art)

Kendo is stick (sword) fighting mate! It does have some attributes you can use but unless the rules of MMA change or you are in a bar that has pool cues handy (come to think of it) i would suggest something else.

Karate - on its own in my opinion is crap, too much emphasis on kata and form, not fluid enough, very rarely fully pressure tested at full speed. Although it will give you attributes you can use to develop your fighting style.

If i was to pick one i would pick Judo and mix it up with a little boxing.

[X]