My analysis suggested that on average the earning rates were similar.

Virgin America points are worth about double Virgin Atlantic miles, so take that into consideration. Your 1 pt/$ is actually 2 miles/$, which is very generous. Certainly, the spend bonus for buying Virgin America flights in cash is very lucrative. I would also argue that it is slightly more valuable in being a Visa, and not everywhere accepts Amex.

That being said, the Virgin Atlantic credit card gives a base spend of 1.5 miles/$ but also gives spend bonus which can cause that miles/$ to max out at 2.1 if you hit $25k/yr. The 1% on foreign transaction fees is pretty good, although if you have a 0% card it doesn't quite compare. However, Amex is way less useful abroad. Also, the companion tickets are not really worth a whole lot, as Virgin Atlantic redemptions in economy are really poor value. Finally, the Virgin Atlantic sign up bonus is way more lucrative.

My advice is to check on the actual routes you intend to fly, and compare redemption values directly. For regular spend, rather than churn, it's close enough that the specifics of your spend and main routes probably matter.