Don't really know anything about the Gateway model. Heard good things about other Heartland models though.
If I was doing any amount of traveling I would not purchase a new fiver without the 6 point leveling system. We didn't have it on our first fiver and I didn't think it was a big deal. We could get completely set up in anywhere from 10 minutes to 25 minutes depending on how uneven the site was.
New fiver came with level up. Now it doesn't matter what the site looks like. We can be set up in 5 minutes!
That may not sound like that big of a deal, but when you have been on the road all day and it is 110 degrees out, it is pretty nice to simply push a button and sip your beer while the trailer levels itself.