Went from LHS Dash-8 to RHS Boeing. Of course this is in the USA, so that's pretty normal here. Different world over here I suppose in that regard, interesting to read this thread and see how different it is out there. Used to be here it was minimum 1000 hours command time in pretty much ANY large turboprop or regional jet to get a shot at the RHS at a major airline. Most regional pilots here would happily jump out of the right seat of a CRJ / ERJ to fly left seat in a Brasilia, etc.
And then, of course, happily jump out of the turboprop LHS to the right seat in a Boeing or Airbus, etc (for a different company, obviously).
These days though, even over here you really need both jet and command time (though the command time could just as well be on a turboprop, with RHS time in the jet) to be competitive. But, if it were one or the other, the large turboprop command would be the more important of the two. Again, only applies to the USA.