Never used the ultra deck, but have used the QuicK Rail system quite a bit and the Vector railing system a few times, Quick Rail is definately better looking and stronger overall, plus easier to install. I don't like the new mounting system as well as the old, but it's still alot better than the Vector railing.
Never used the "ultra decking" nor the "quick rail" before, but would do so in a hearbeat if things could be reversed. I've got a large deck out back, plus a 50 ft front porch made with standard [wood] treated decking materials. There's no serious problems with either structure, but the hassle of annual maintenance plus the floor boards struggling to curl up against the 3" screws makes us wish we would have paid twice the initial cost at the onset. It hurts just one time .... at the beginning ... but then the homeowner can forget it and enjoy it.