I have the 12-20 Jet, without VS. It has been a great lathe, but a PITA to change the belt. I have turned on the 12-20VS and the Delta 46-460VS and like them both for different reasons. Both require belt changes for speed ranges. It is a lot easier to change the belt on the 46-460 since the door opens in front. Other than that they are both great and make exceptional starter lathes. Limitations are length and the limited swing should you decide to make much larger items than pens, bottle stoppers, and small bowls.
I have since gotten a larger lathe for the reason of size and no belt changes for variable speed. Wish I had done that from the start, but I don't regret the experience and enjoyment of my original Jet. It does make a great buffing station and for drilling pen blanks.
FWIW. It comes down to what you want to put into it ($$) and what you want the lathe to do for you.
Happy Turning!
gordon