What a complete load of bollox!
You won't find many TRIs or SFIs who would support www's point of view. It's immediately obvious whether a candidate for a first multi-pilot type rating has received good or bad MCC training, and those that have received good training find the type rating course streets easier. It matters not one jot whether you do the MCC on a jet or turboprop, it's only the quality of instruction that matters. However, I lean toward the school of thought that says you find it less of a culture shock transferring from piston to turboprop and can concentrate more on the job in hand, but then I never had to do a MCC course so what do I know?
Having experienced the output of most UK MCC providers, I'd say you'd be hard pushed to beat Jetlinx - who just happen to use BA's sims at Cranebank (although I'm sure their product would be just as good if they used a FNPT II but not, perhaps, two upturned orange crates.)