My favorite thing about the older SMTs is the way that your options are always a little more limited. In Soul Hackers you can't afford to haul around a huge party of summoned demons all the time, SMT1 and 2 have stricter alignment requirements and conversations are generally harder, and I think in SMT1 you also had the Macca cost for summoning demons (But not maintenance..?) -- stuff like that. In Persona 3 and SJ I never felt like I didn't have a party that could deal with everything. In SMT1, I felt like I DIDN'T have that luxury, and a lot of times I had to deal with situations using whatever I had. And that was interesting.
By the by, with regards to SMT1, is it just me or is NPC placement a lot more reasonable than in Strange Journey? Like, I know you can't see the NPCs on the map, but it followed the PC dungeon crawl convention of either sticking them at obvious locations, like tables, or in chokepoints. In SJ they could be in the middle of a huge empty room and you'd never see them without stepping on everything. And this got annoying with some of the sidequests.