Kamui only has a reputation for crashing because he overtakes outside the DRS zone, and isn't afraid. From memory, he's only been involved in an accident twice - Belgium '11 where he crashed with Hamilton, and Canada '10, where he crashed into the Wall of Champions.
Any others I've missed?
Checo seems to crash a lot more, and is therefore much less consistent with his points finishes.
He crashed in Singapore during 2010.
Which, like his crash at Canada in the same year, was the first time he'd been to either track. Important to point out that many other incidents he's "been involved in" weren't his fault. Genuinely. His crash with Hami in Belgium clearly was not his fault (as Lewis later admitted), neither was it his fault when Schumacher piled into him at Silverstone in the same year. Same with China '10, on the opening lap, a spinning Liuzzi took 2-3 cars out including Koba. And to call the Australian 2010 race his fault is unfair, Sauber had major front wing problems (two came off in the practice before the race) and it came off going into turn 5. The only two incidents I can really remember where Koba has taken someone else out were 2009 in Brazil, his first race, when he moved over a little late on Nakajima, and in Singapore when he and Schumacher came together.
I've long held a belief, rightly or wrongly, that Koba gets an unfair rap based, it seems, on his place of birth. Japanese drivers have in recent memory had a reputation as being 'wild' or 'crashy'. Nakajima did make a lot of mistakes and crashed a few times, and unfortunately, that has stuck with Koba, I think. When you look at his list of DNFs, most of them for Kamui have been mechanical faults, not his driving. It always irks me when people say he was poor in the beginning of 2010 - well, the car didn't hold up for several races, and when it did, he was consistently in the points.
Which is not to say that Perez is much of a crasher either. He's had a couple of opening lap incidents but nothing too severe.
I think they're both significant talents in this generation of drivers. Out of the two of them, it's easier to imagine Perez will have the better career - he's a couple of years younger, he's easier on camera, has a lot of money behind him, has the Ferrari link, and is the 'bright young thing'.
As much as I hate to admit it, I find the idea that Koba will find himself in a top seat unlikely, which is a shame because I think he's an absolute joy to watch and a driver whose character really shines through into his driving and his racing.
And, despite his 2nd place at Malaysia, Perez is just now 3 points ahead of Kamui. It's going to be a very interesting season.