I'd say play 4. The gameplay is just as solid as in 3, and it's really part of the appeal. I definitely wouldn't skip on it if you're enjoying this series, as the thing has so much choice going on that watching it on Youtube just feels like a waste.
Also, if you're interested, it could be cool to follow this order:
P3 > P4 > P1 > P2IS > P2EP > P5
But this is mostly if you're interested in the series' roots. 1 and the two 2s don't have social links and play more like traditional dungeon crawlers, but they're still very interesting, with the 2 duology having arguably the best plot in the entire series (I've yet to play EP so I can't really comment on that notion, but Innocent Sin was definitely some good trout while P1 is an acquired taste but definitely worth checking out).
There's also the issue that P5 follows the same formula as P3/4 BUT also reintroduces some elements from the previous games (demon negotiations, more elements, some visual cues) that will probably make it feel much more like a culmination of the entire series if you know all the other games first. Fun fact: all Persona games take place in the same continuity, even if call-backs from 3/4 to 1/2 are minimal at best.