If you are deciding between either a S12II or a seasonic focus, spend a bit more and buy the focus.
It is a newer gen power supply and will be long term product for you.
Really either would be OK, but on a psu, buy the best.
Generally speaking, in a mystery PSU, you want OCP largely because in the aggregate, PSUs without OCP are going to be crappier than the ones that have it. Not every person with a Porsche is rich, but if all you know about a group of people is whether they own a Porsche and you have to guess who is rich, you'd guess the guy with the Porsche.
On a known PSU like the SeaSonic, it's less of a big deal. We know that it has competent protections otherwise, so while you'd like OCP, we already know it's a safe, fairly competent PSU, though of older design.
It's important to remember that ATX spec used to not allow more than 240 VA on any given rail. So you absolutely had to have OCP at that point. That was dropped and so it's less important with bulky single rail PSUs with functional protections otherwise. Again, knowing nothing else about a PSU, I'd take one with OCP over an identical one without, but it's not a deal-breaker in this specific case.
Note that the I'd absolutely buy the Focus too. But in a situation in which one can't really spend more than the SeaSonic S12 II, it's not some fire hazard.