If you like just a direct answer to your question,
If you could only pick one, which would it be?
For me is very easy: PAM 388. I got a PAM 388 and I have not bought yet a PAM 380
Then my clear option: PAM388 without doubts
But I think your decision should depend on your taste and requirements.
Let me to guide a little asking you some questions:
1-What do you prefer manual or automatic?
If you are not willing to wind the watch every day (o two) PAM380 is not your watch
2-What do you prefer display or solid caseback?
To answer this question bear in mind that a display caseback is very nice but allows to tell the movement flaws.
3-Is very important for you movement accuracy with a display caseback?
In this case you cannot buy a PAM388
4-What do you prefer about thickness: 15mm PAM380 or 16,5mm PAM388?
5-Do you want date? If yes you need a PAM388. Otherwise go to PAM380
6-Can you stand a Radiomir with date? If not you cannot buy a PAM388
7-Can you stand a flaw on dial like PANER_AI space? If not you cannot buy a PAM380
8-It is important for you the OP logo? If yes the only option is PAM380
9-Do you like the combination of soft colours in PAM388 dial, with slightly greenish lume and soft creamy inscriptions and date, like modern Panerais come, or you prefer a more uniform colours like old PAM 380?
10-Are you looking for the best finish and gen appearance? Then KW PAM388 is your watch
11-Are you willing to can get problems with lug screws? If not you cannot buy a Radiomir either PAM388 or PAM380
Reply by yourself above questions and you will be able to get a decision
Good luck
ALE