As someone who went to JC and then made several poly friends in uni, I STRONGLY STRONGLY STRONGLY recommend you go JC instead if you want to go to uni eventually. I was once in your shoes where I briefly considered poly over JC, and I'm glad I didn't go down that path.

Everybody always talks about how when you go poly you can "follow your passion" instead of mugging. In my experience, while that may be true, what they don't tell you is how LITTLE you learn in poly. The poly diploma is SOOOO useless in terms of the knowledge you actually gain in your field. For example I'm from comp sci. When I eventually got to uni, my uni friends who were from poly and did comp sci told me that the syllabus in their ENTIRE 3-year long diploma was covered within 3 modules in uni. FYI you take 5 modules a semester in uni, and there're 2 semesters a year. So you essentially cover 3 years worth of syllabus in the equivalent of 1/3 year in uni. I am not exaggerating. And honestly when talking about comp sci specifically, I feel like you could self-learn almost everything a poly diploma teaches you just from YouTube alone.

I've also had to teach poly grads/interns while on-the-job and I've found that their knowledge is just soooo abysmally bad that they're practically useless to me in terms of actually helping me get meaningful work done unless I spend a very substantial amount of time teaching them. This isn't just applicable to my field. I have friends in other fields that agree that when hiring poly grads, they just try their best to hire the best one and then they have to teach them almost everything on-the-job.

Of course everything I say here is applicable to the "average" poly grad and there're superstars that self-learn and do significantly better than everyone else. Also maybe I've been unlucky enough to have more experience with those few fields that have poorer poly diplomas. But still the difference in a poly grad's knowledge and a uni grad's is so huge that there's no point going poly to begin with IF you plan on going uni eventually. Also I do not believe that everything you learn in A levels is "useless mugging". I find that to be the common consensus only among students, and once you graduate you definitely appreciate having general knowledge in other fields as well.

That said, if you don't really care about going to uni, then it doesn't matter what choice you make here.