cass ... A couple of thoughts ...
First, you can lead a horse to water, but if he drinks, that's his decision ... Your friend made the decision to buy the Pa600, not you ... Did he expect to find the same styles? Was that a realistic expectation? ...
He didn't spend enough time on the 600, is he going to spend enough time on the 700?
Your friend needs to spend the time researching the 700, including playing it, before he makes his decision ...
You can only relate to him what YOUR experience has been with the 1000 ... Make sure he knows that any decision he makes is his and his alone