I happen to own an old copy of Real Flight 3.5, and I wasn't impressed with it from the get-go, because the helis were always so minute in appearance, and lacked the exquisite detail that Phoenix4 offers.

I have no idea how the later versions of Real Flight stack up against Phoenix4, but I never bothered to acquire any later versions  than RF3.5, which is now gathering dust in a desk drawer, while I log may hours weekly on Phoenix 4.  There is no comparison between the two, in my opinion.