I just got an Ultra Dot 30mm in an eBay auction (that was supposed to be a Tasco PDP2, oddly enough). I shot with it this weekend and compared it to a few other red dots. It worked perfect for about 50 shots, but the recoil on an AR-15 isn't exactly stout. All in all, it seemed to be of much higher quality than the other lower priced brands, but I wish it has the brightness adjustment knob on top instead of on the side. That and the lack of ability to adjust the size/shape of the dot are the only things I can think of that could be better. I was trying my best to criticize the scope, too, as I was deciding if I wanted to keep it or send it back to the guy that auctioned it as a PDP2. I'm definitely keeping it and would probably buy another.
I haven't heard of the 4X Triail scope before, and the only things I've heard about the Burris Speed Dot were bad (wouldn't hold zero). Sorry I can't be of more help.