Out of what? cause the first two have no real connection to the second two. They become VASTLY different games, and the games that most people here like to praise are Persona 3 and Persona 4.
Now me personally, I've played both, multiple times, and loved each. However, I enjoyed Persona 3 more (and if you get Persona 3, get Persona 3 Fes, cause there's much more in it). I enjoyed the story, and the characters more then I did in Persona 4. And while it is one dungeon in comparison to Persona 4, each one feels distinctive in its appearance, and the enemies do as well. Plus the reaper looks cooler, it seems, and there seems to be more fulfillment in Persona 3 Fes' ending then in the Persona 4 ending(s).
Plus you get the Answer in Persona 3 Fes, which is like two games in one, and you get the extra 30 hrs. So there'sa bit more gameplay in Persona 3 Fes with the 100+ hr gameplay of the Journey, and the 30+ of the answer.
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ANd you cant deny that Orpheus Telos is freaking amazing.
So, hence my avatar I suppose. XD
EDIT:
And actually, thinking about it now, You should probably play 3 before 4. Its serves as a nice intro to the battle system you use in four, so there's a nice transition, and some of the jokes and characters you see in 4 are from 3, so just knowing who they are or why its funny is nice.
... come to think of it, one of the main jokes in one of the S. Links in P3Fes was from P2...