I don't think you're considering how useful it is to have an amazing cheap (once you have the CC) defense that takes up no supply and doesn't require any supervision. And 40 splash damage per second... that's friggin amazing. Yup, the same argument has just been repeated for the 100th time, but that's probably because it makes sense.
Now, yeah maybe they'll nerf the OC and buff the PF's stats (which might mean the PF is inferior to the OC right now), who knows, but we aren't talking about specific stats, we're talking about concepts. And sometimes you need a quick efficient defense, and sometimes you need some attacking power.
So imo, it's dumb to compare stats since lots of stuff might still change, but the concepts are both rather unique and interesting. I definitely don't want to go up against a forteress when I'm attacking a random terran expansion, that's for sure (esp. if there are 20 SCVs repairing the thing, making it indestructible).
I don't know how much a PF is, but isn't it possible to build a CC (400 minerals) plus the PF (I'm guessing it's around 50 min/50 gas) to defend a choke point like a ramp? Considering a bunker already costs 300 minerals (4 marines), 450 min/50 gas for a defense that takes no supply and is much stronger seems like a fair deal.
I think the planetary fortress is 150/150 (IIRC).
So that's actually 550/150.
Quite a considerable amount more, with no ability to be salvaged.
Immobile as well, so the only points it's ever going to be useful is on those yellow minerals, and even that will probably be questionable.
Losing a command center and having to pay an extra 400 minerals to get a new one, (or 550/150 to get another Orbital Command) plus the amount of time that takes would be worth it to get a planetary fortress. Especially with how open the area around those gold minerals are.
True, and by that time you'd probably have one or two OCs at your other bases, so Mules wouldn't be too hard to get, if you were prepared to risk them.