In comparing the two systems, I'd have to say the outstanding difference is Salvo's concentration on squadron vs single ship action. Also, the interface is much different. Read my preview at subsim.com.
Jim, about your preview...
I really enjoyed it, thanks for taking the time to give us a look at the game. One quick thing I wanted to point out though, is that you didn't list the Mac requirements at the en d of the preview. Minor point, really, but you never know who will be reading.