Ultra Tight Timings...thats funny (and mostly accurate, too).
It actually stands for UnTestTed.
These ICs are sold to the module manufacturers without having been tested nor binned. It then is up to the manufacturers like OCZ and TwinMOS, for example, to test and rate them.
Whether they are better or not depends on how good they are, for starters, as not all of the stuff used in value PC3200 will run 250 at 2-2-2-x timings. It requires gobs of volts so if a person is limited to something like under 3.0v, TCCD would be a far better choice. With TCCD you can run tight timings at the lower speeds and then run 270 or more with relaxed timings. The UTT stuff, as a general rule, will only go so far, even with relaxed timings.
The DFI plays nice with just about any ram currently available so either one would be good. Keep in mind that the UTT in the value ram is more of a gamble as it has not been tested or rated at anything over 200 and then, its with relaxed timings. You have a very good chance of doing better, but no guarantee unless you go with a product like the OCZ VX PC4000 or perhaps wait and see what the new Mushkin Redline will do.