When 5150 came out, I didn't care for it at all. "hate" is a bit strong, but I surely didn't like wtf I was hearing from the band or Hagar. OU012 vastly changed my opinion of the "Van Hagar" era. The singles on that album were good, some very good. Black and Blue is still one of my faves. Cabo Wabo has a great groove to it. Finish What You Started is a fun track that we haven't ever gotten enough of from VH over the years.
OU012 easily gets my vote here. Over the years, I did warm up to 5150 and enjoy much of it now, but for me, it can't beat its successor.