I just had a quick look. The Compare feature on the Jayco site, yes, only shows the water tank (That 90 gallon tanks is a great asset on the trailer) as the only difference. But if you look at the standard features on both models you'll see quite a few extras that the Jay Flight has that the Swift doesn't.
Some I noticed were
-30 lb tanks (swift has 20lb)
-Spare tire carrier
-Tub skylight ( great for us 6ft'ers)
-Outside shower (great for kids and Dogs) also good for when your boondocking and don't want to fill up you grey)
The best thing for you to do is look at both in person. You will see why the Jay Flight is 3-4K more than the Swift. IMO if your looking at the 19rd, you may as well look at the 22fb as well. The price is only about $1000. and you get a whole lot more trailer. You'll need something with at least 6000lbs towing capacity to pull any of these trailers (more is always better as you'll find out on this board when it comes to Tow vehicles)