Both classes are bad, really.
Get a monk instead, no reason not to in 90% of situations. Yes, knights have cool tricks for certain narrow circumstances and emergencies, but look at an entire 9 hour grind session or whatever you are doing... you're going to miss the monk's dps, and having more dps will probably save the day just as many times as having clutch abilities. Most knight utility gets eclipsed by shamans and enchanters, and those classes are ubiquitous. DPS stacks endlessly; you can never have enough.
This has more to do with monks being overpowered pieces of shit than anything, though. That's my perspective, it made me really unhappy playing my SK at high levels. Monks have great agro, great mitigation, great DPS, great utility.
Grrreat! Fuck em.