Double ended lamps don't have much on a good setup with your typical e37 mogul.
I said not much because a good hid setup runs at high frequency, same as gavita.
A good hid setup runs low thd (this is where the double ended lamp shines a little better)
With a e37 mogul the electrodes have to run parallel to one another, the dual ended does not. This surely creates a more quality light but is it all that much better than conventional high freq ballast and e37 mogul. Slight edge is all there would be in my opinion but hey, I don't design lights for a living.