But I highly recommend playing EP after IS. Just not right after since some of it is a retread.
I played the games in order, both on the PS2 via BC, IS in 2005 and EP one year later. EP still felt like a major retread and I cursed the story (which was interesting enough) for making me play through all the same locations again, with the same gameplay, just harder.
It is true that IS is very easy and EP should be the more interesting game thanks to being more challenging.
But IS was fun to me for finding the fusion attacks, it was fast because of the low difficulty and auto battles (which featured heavily in mainline SMT also but are much nicer in P2, thanks to fusion attacks and the way it's set up), it didn't have a crazy encounter rate on PS (but dungeons got too long near the end) and the negotiation system is one of the best in all SMT games (and the spin offs that use it like P1-2). You could switch between battles and negotiation if either got boring and the story was captivating so I just pressed on.
The higher difficulty in EP demands a more strategic approach but it is easy to find a strategy that breaks the game. Exploiting the boss's weak point is almost always the best way to defeat it in a few rounds, and since I often only had one (or two) personas that could hit its weakness, I constantly unequipped and equipped it to the next party member. That makes a few rounds take quite long and un-autos the battles to make the process rather tedious but it worked every time.
The thing is, since IS was new gameplay to me it was interesting to learn the systems. Towards the end you already understand all the mechanics and nothing new is added so the game starts to become boring. It's like that for most RPGs.
If difficulty results in the need to apply varied strategies that's welcomed but after IS, rushing down EP was child's play. So the higher difficulty just made the game more tedious.
As for EP's story, it is supposed to provide the adult perspective on the original's story. That it does quite well actually but without IS as the reference point a lot of the impact is lost. IS really has all the impact.
The rumor system may not be as refined in IS but it is meant to demonstrate how our construction of reality can be so out of touch with the facts. Prefering the more utilizable rumor system in the adult world EP is like appreciating how you can manipulate people with narratives you spread (formerly a tool mostly of the mainstream media but increasingly gaining power in social media).
Persona 2 illuminates this to guide people towards facing the truth.
Tadashi was way ahead of the curve.
It's always weird to me when people refer to a person they don't know personally by their first name.
As for Tadashi Satomi's acccomplishment as a JRPG story teller, I think he, Masato Kato and most of all Kazushige Nojima are Yasutaka Tsutsui's most prominent (unofficial) disciples in the game segment of Japanese culture. Tsutsui is the author of The Girl Who Leapt Through Time, a Japanese youth SF story from 1965 I mentioned earlier in the thread. This story was remade in various media again and again and is influencing writers to this day.