I have made some pretty excellent "to style" witbiers with different yeasts. While I haven't done this with 550, I am confident it would work. My all-time best witbier was actually made with Wyeast 3711. I also used the Unibroue strain effectively, as well as 1214 (to-style, but not my favorite). One strain that I have stopped using for wits is Forbidden Fruit, which is actually listed as a good strain for Witbier.
One strain really REALLY enjoyed in a session ale, which I plan on trying in a witbier was 3739. It was a very spicy, phenolic strain, giving an almost cinnamon-like aroma to the beer I made with it, and I regret not keeping that yeast strain going longer.