A couple of thoughts from my end:
I have done both JFK-FRA and FRA-JFK and think JFK-FRA is the better flight: full dinner, caviar service and you can sleep for a bit on the overnight flight to give the double bed a try.
Virgin Clubhouse is a great lounge and better then the LH Senator Lounge in Frankfurt.
The Private Room is very underwhelming compared to most flagship offerings of other airlines. I would not recommend to make any effort to include The Private Room in your virgin flight.