I have no experience with the scissor lift; in fact, I had no experience at all until I bought my trailer.  I got incredibly lucky and found one on EBay less than 1 hour from my property with a Buy It Now price of $1,800.  Since I had been looking for some time, I didn't hesitate - I had it bought, paid for and back home long before the auction was due to end.
It's a 6' x 12' U-Dump with 12,000# gross.  I've had it to the landfill a couple of times, so I weighed it on their scale, and the empty trailer comes to about #2,600#.  It has a single cylinder lift to about 45 degrees.  The hinges are about 2' forward from the back of the trailer.  It dumps lighter loads effortlessly; I haven't had it full of dirt, yet.  I've been doing some remodeling and have been hauling wood, drywall, etc., to the landfill.  Once I have it tilted up, I climb in the truck and drive forward rapidly, and it all emptys out.  It goes up so easily that I'm sure it will handle a full load of heavy material.  Legally, I won't be able to fill it full of dirt -- it measures out to hold about 5 cubic yards struck, but that much dirt will weight about 12,500#, so it looks like the most I can carry and stay close to the weight rating is 4 cubic yards.  It is gravity down with a flow control, which is nice, especially since I have no cold weather to slow it down.
Why so cheap?  It isn't perfect.  It has a single swinging rear door, and the hinges are slightly bent - it fits well when closed, but lowers to a drooping position when swung open and hooked to the side of the trailer.  It also has some rust -- one side of the bottom has rusted away.  I needed to use it right away and didn't have my welder set up, so I bolted 3 - 6' x 4' pieces of 3/4 plywood in the bottom for a temporary fix.  Two of the tires are marginal.  I spent $18 for two new sealed bulb inserts in the Wesbar sealed marine taillights, and $10 for a new wiring harness.  I also spent $20 at Wally World for a little automatic trickle charger that mounts to the side of the battery box, and I plug it into an extension cord every once in a while.  I do have a charge circuit wired up to my truck, but I don't tow it long enough to recharge the battery.
Still, at the price I paid, I'm ahead of the game.  The electo-hydraulics are fine, the battery is good, the 4 wheel brakes are good, the frame is straight, the dump hinges are fine, and once I weld in a new bottom, put a coat of paint on it and install a couple of new tires, it should be worth $3,000 or more.  I'm very pleased.  Of course, beggars can't be choosers, and I'd have accepted worse at the price.