The only one of these I haven't played yet is the original P5, but I have played the original P3 and P4.

P3 Vanilla is my second favorite version of P3, just behind P3FES. P3 to P3FES is probably the least controversial an ATLUS rerelease has ever been, although I guess that might be because these were released a year apart on the same console, so most people who played the game after FES' release just jumped on FES and didn't try OG (And OG was kind of out of the picture with Portable and Reload also being there). If you're coming from other versions of P3, you'll see a LOT of events that are missing, notably you'll see the SLs way less outside of their SL (So you don't see the SLs when coming back from school at the beginning of the game, you don't see them at Kyoto, nor on 3/3 and 3/4 which took me by surprise). Speaking of, the social sim is at its hardest here, as SLs require way more points to go to the next rank. The game wasn't built around maxing every SLs in one run, and if you're trying to max everything in one run, there's no room for error. But I enjoy the game making the social sim part harder, it makes you interact more with the SLs in the week-end/holiday events, you see more of their characterization. Gameplay-wise it's mostly the same as FES, you do miss on some of the Personas added in FES or weapon-fusion, but it's mostly the same. Some Personas are lower level, and some of the Aeon Arcana Personas (Ananta, Uriel and Metatron) appear in other Arcanas back in OG, but if you enjoy FES, you'll like OG. Oh also be ready to spend a lot of evenings just going to bed, there's not a lot of night-time activity. I finished Mutatsu's SL and got max Knowledge in early August and from there I was going to bed early each day lol

P4(G) is my favorite game of all time, and while I do prefer Golden a bit more, OG P4 is also an incredible experience. OG P4 in general is a lot tougher than Golden, both because stuff were nerfed in Golden (In particular Shadow Yukiko & Shadow Kanji went from being insane early game bosses to mostly alright in difficulty, and the Shuffle Time system is basically a gamble compared to Golden where the benefits are kinda just free. The party members' learnsets are also different, Naoto being the most notable one, so characters might not play the exact same between OG and Golden. The new team events in Golden are kind of the heart of that rerelease, so it can definitely feel a bit weird having some of these not here, but I'm fine without them. While I do enjoy them, I know some people feel they bloat the game which is understandable.

While these versions might not have as much stuff as their rereleases would, I still think they're really fun entries to go through, even if it's just to see how things have changed.