Err...I can't say for sure. Caramon is stronger, in all I have say I'd go with Caramon. Sturm can't beat him...to me, at least. Caramon is a bit slow on the uptake, but he shouldn't need brain power to beat that Knight. After all, with Sturm the fight would "honorable" so there shoudn't be anything Caramon has to stress himself about.
Err...this would be a case of 'my god is better than yours', but since they both supported the same god...I'm going with the Kingpreist. I vaguely know his story - haven't got around to read the Kingpreist Trilogy yet - and it seems he could kick butt - compared to Elistan - as far as clerical powers go.