I've never used Optimum so I can't provide a direct which is better answer. I can say that PG works well but does have a learning curve. In my experiences with PG, it dries out pretty quickly, long before it's really broken down, but if you spritz the pad with water when it starts to dry you can keep working it. It does work very well, it's also very abrasive.
I recently used both on a detail. The power gloss compound does dry out rather quickly but has good cut and leaves very little residue and is easy to buff off leaving a nice clean finish. The Optimum compound is pretty good and has a good working time and pretty decent cut but I was not happy trying to get all the residue off and mandated an IPA wipedown afterwards. Both are very good compounds in my opinion and you should be happy with either or both. I have used PG more than Optimum and it is a mainstay in my arsenal.
I'm an avid OC user. I also have the Menz PG, and it does work nicely, but like some have said it dries rather quickly. I can work OC a LOT longer, which helps me get the correction I need done without having to stop, spritz pad then continue. Both are great products, I just like to work with OC more.
Two different animals. PG is a 1000ish grit leveler, it cuts hard but it gums up badly and is a generally unfriendly compound (the new generations are better).
OC is a dream to use but its level of cut leaves a lot to be desired on those really bad jobs. It does have an exceptionally long working time, which can be a good or bad thing depending on your personal preference.
I would reccomend looking into the XMT line. In my experience, they are more PC-friendly than the competition.