yes a ppl pilot can fly a Bell 407 but make sure (s)he`s got an experienced safety pilot with her/him
This almost certainly going to be the case unless one self-insures. Most insurance companies are going to require substantial SOE plus frequent recurrent training before turning a less experienced pilot loose solo in a 407. OTOH, a compelling case can be made that the R22 is a more challenging/demanding acft to fly than a 407. Broadly speaking a turbine engine makes life easier for the pilot, even the low time pilot. IMHO, too much is made of the transition from piston helicopters to turbines.