Karma is what we think we want to be in control of the universe, because we think we are morally good people, and will be rewarded as such.
But by what standard are we comparing ourselves? To me, taking the ego crunch of admitting yourself as a failure, and then being both instantly redeemed and progressively reformed to a new life seems more appealing to me - simply from a cost/benefit analysis alone.
Throw in the evidence for the resurrection in there, and Jesus wins in straight sets.