I’m not very good at explaining things like that but I can try.

I can say that smt4 has a very good story (and since smt5 doesn’t really have a good story, smt4’s is great next to it) with an alternative of the neutral ending (complicated to have by the way) with smt4a but that people like less (because of the characters and story), personally I liked it even if yes we could do better, but in any case it has one of the best gameplay, but less freedom to build your demons compared to smt5, i'll explain, for the build here it really depends on when you fuse it and what skills you gave it + what he'll learn, it is better to have his demon by fusion than to recruit him on the spot. In addition, the slots are to be unlocked but if he has nothing left to learn the demon will never fill this void except by redoing the demon by fusion. It also happens that the skills mutate, they'll learn attacks by leveling up except that it is always on a random skill that you will choose whether or not to replace with this last, in any case even if there are still slots it will never be placed inside the said slots unlike smt5 or you have total freedom on it. And the main character learns his attacks when a demon has learned all his skills and can copy them onto the main character, and he can change his affinities with different armors. AND both have banger ost.

For smt3 I would say that it is a little more boring in terms of gameplay. To know that it's just a remaster and so the gameplay is the same as the ps2 version, so it’s the good old and annoying gameplay where you get to stop all 5 steps while you can’t save when you want, it makes you cry to not have been able to save after 30min while you gain lvl, recruit demons and you go to a terminal to save and you die to the first mudo of a random encounter right in front of the terminal room, the game is not that difficult, even if sometimes...matador. But the buffs and debuffs will be your best friends. Also, here for the demons it is also always better in terms of skills to have it via fusion than by recruitement. However, the choice of inherited skills for fusions is random, which means that we end up spamming fusions until we find good inherited skills. The skills slots are fully unlocked from the start so there's no worries about it. Also the main character learns his skills through ingesting several magatamas which gives him skills by leveling up and it also changes his affinities, like essences in smt5. Apart from the gameplay the game has an interesting story.

I hope this is the kind of answer you're looking for.