In a 235/60-15 size, the only worthwhile tire I know of (at Tirerack) is the Michelin Pilot XGT H4. While Dennis (Q45Tech) has very good things to say about this tire, I am very biased against it, due to my terrible wet weather experience with the Michelin Pilot XGT V4 ... which, admittedly, may be enough different from the H4 to not be an issue.
Of course, also note Dennis's pro stance above on wet weather behavior of the SZ50.
The SZ50EP is a change from the SZ50, but is still the best that I can think of for the original criteria mentioned: wet weather performance in Houston.
Z