I haven't flown enough helicopters to have a definite answer.
With most helicopters only having a centrally located collective, I found it easier to handle the 'more critical and twitchy' cyclic with my right hand, and the 'push-pull and twist' collective with my left hand, hence flying from the right-hand seat to me made sense.
On the other hand, my instructor in the LHS had no problems in that position, so I suppose it's not really a great deal.
Cough's, Admiral346's and P.Pilcher's answers in particular seem to confirm that.
CJ
BTW Think of manual-shift cars in town traffic - you do almost as much shifting as you do steering, with one hand almost permanently on the gearstick. I've driven both in the UK and in France for years, and I don't really have any recollection of one being any more difficult than the other.