Yep, kneecaps are nasty ones without a doubt (and it entirely depends on the extent of the soft tissue injury), but there is at least proper bloodflow to the surrounding ligaments. Rupturing your cruciate also has a high chance of recurrence. There's actually a relatively recent developed technique to stop kneecap dislocations involving deepening the knee groove, so there are ways of improving it.
The key though is the long-term damage it does to your ability. With a cruciate ligament injury you're unlikely to fully recover - an average of 5-10% loss of power in that leg, difficult to fully build up the muscle again, etc. Also there is statistically (bizarrely) a higher chance of cruciate ligament injury on your other leg after you have had one (because some people are more susceptible). Basically, with a cruciate ligament injury, there's no easy option. Look at what it did to Michael Owen. Fortunately, pace isn't really Snodders' asset though!
Don't get me wrong, kneecap injury is nasty and (as we don't know the details) could be very, very nasty, but on balance this is better than a cruciate ligament injury as there is a higher chance of 100% recovery. It all depends really on information we don't know, admittedly.
Mind you, the sports specialists are very good these days, especially the ones hired by the clubs so no doubt he'll be right as rain in any event. Here's hoping
