One friend ( who owns a largish helicopter company ) is of the opinion that the 600 seems to have an inordinate number of blade to fuselage strikes during aggressive maneuvering. Some of you may have operational experience and disagree.
The 407 is a really sweet machine... Hoping to maybe start flying an IFR one... But they are certainly not an inexpensive machine to purchase and fly... The R66 can be a good and inexpensive ( as turbines go ) to buy and operate ( but lots of people here will warn you about the low gee characteristics which I think are even worse than the R22 and R44 when the R66 is at low weight ( like when I'm low on fuel on a gusty day I tend to fly the R66 pretty slowly ). Still, when operated properly, it's an economical turbine helicopter to fly ( but if the guy is considering 407s maybe he doesn't care about the money!).
I only have one flight in the 505 ( at the factory ) and I agree that's a machine worth considering... Lots of nice attributes...