It depends on if you believe Caedus is capable of driving back Vader as swiftly as Luke did. Given Caedus' ability to stand well against an enraged, albeit somewhat injured, FotJ Luke, I'm certain he'd have an easy time with RotJ Luke's onslaught.
Also, given he's more powerful in the Force and has more esoteric abilities at his disposal, I'm liking Jacen's odds.