They are different types of equipment.  The Ultimate is a snappier ball, with a more definite, angular move.  It, like most reactive balls does not handle hard carrydown or really create its own backend.  If you have soft backends or if you need the ball to "catch" in oil, the Warp Zone is better.

However, the Warp Zone MUST be kept clean and dull -- the coverstock will tend to "glaze" over after every few games.  To keep it at its best you need to clean it with something like clean n dull or hook it AND periodically (about every 10 games) go over it with a burgundy scotch brite pad -- I do it while cleaning, applying Clean N' Dull with the scotch brite pad and then wiping it off with a paper towel and then cleaning any left over material with a pure cleaner/degreaser.
--------------------
"I don't mind if you don't like my manners. I don't like them myself. They're pretty bad. I grieve over them on long winter evenings."