I live close to MAN and have taken the LHR-LAX VS flights several times in the last couple years. I agree with the comments about enjoying the VS Clubhouse, but for the first time in July I will be taking the MAN-LAX flight and return.
The travel to Euston, then car to LHR on top of an already long flight is just too much for me to not switch over to the MAN-LAX flight, I'll take any reduction in travel time I can.