Answer:
I'd have to see the two lathes to tell you, but there are four main reasons a turner replaces his lathe: the new one vibrates less, the new one is larger either in length or in the diameter of the piece it can turn, the new one has a bigger motor, or the new one runs at a slower speed than the old one.
You're asking yourself "wouldn't you want a faster lathe?" No! A turner wants a lathe that has lots of power at slow speeds because it's safer to make the initial cuts on a piece at a really slow speed, and the slower speed will let you make turn larger pieces.