Just in case you don't get a reply from an expert; I can offer my own (inexpert) experience with the Virgin Atlantic American Express Card from Bank of America (possibly the longest name of any credit card). It puts Flying Club Miles into Virgin Atlantic's FF program and it is easy to book rewards on the Virgin Atlantic website. To use Flying Club Miles for Virgin America rewards, you have to call the Virgin Atlantic Customer Helpline. That's a little more convoluted and involves the agent in contacting Virgin America. Then Virgin Atlantic gives you a reference number which seems to be alien to Virgin America. However, it all seems to work out OK (I just booked LAX-SEA successfully and then got Virgin America CS to reserve my seats.)

As you say that you want to make your reward redemptions on VS, I'd go for the VS credit card and Flying Club. I guess that the alternative of VX and Elevate points would mean that booking VS rewards would be a bit involved.