Both have their problems. First OCAL
Ocal has a problem with the coating. Last year we were having problems with the outer coating splitting when you bend it. Some of it would just ripple really bad some would flat out split in half. We returned thousands of feet of 3/4" and 1" pipe because unless we were installing it on a straight rack it was useless.
RobRoy doesn't have the coating problem and is a very good quality product. However, it is sometimes very hard to get. Especially their fittings. We got into such a pickle on my last job we used allot of OCAL fittings with RobRoy pipe. We were not supposed to do that but when the wait was sometimes more than 8 weeks and over 100 men to keep busy we had no choice.
My vote is for RobRoy if you can wait.