Eaz-Lift started the whole W/d hitch back in the '50's. Their system was the bent bars and patented so for fourteen years they were the game in town. Patents expired and everyone made W/D hitches and funny they still look like the Eaz-Lift today. They all claim to be better mousetraps, but they still do the same thing. And it's a good thing!
The Hensley and Pro-Pride are magnificent W/D hitches and if you have a large heavy trailer consider one of the two. Your considering a 4500/6000 lb. trailer I would go to your local hitch shop and brainstorm with them. Make sure it's set up properly (most important). When they're set up properly with the ball angled down towards the back, it doesn't look right IMHO but the angle is critical. Don't go overboard with your spring bars i.e. 1,000 lb. bars the ride will be bone jarring in your case! You will shake your trailer apart.
The way to judge the proper spring bars is to jump up and down on the bumper of your truck, if you can make it move, you want the same travel when the trailer is hooked up with the W/D hitch. The spring bars are supposed to act as springs and transfer weight. On miles of ad roads you will appreciate the ride.
Good luck with your TT.