I feel that contribution should be equal irrespective of class difficulty. I gravitate towards tough MMO classes and overcoming the challenge is it's own reward.
That said, I'm pretty miserable in having chosen SMN/SCH for 4.0, as both are clunky and a bit dull. Also, SMN quality of life for solo content has been considerably reduced by having zero pet heals (your coconut doesn't even heal them!).
The focus should be making all classes have a similar damage/utility aggregate ceiling and then focus on improving the enjoyment of each.
