I'm definitely a fan of paci vs thumb. If you get a little pacifier clip, you can clip the paci to them. In the middle of the night, when it pops out, they just grab it and put it back in. It doesn't get lost since it's clipped on them. When they are really little, sometimes I have had to go back in a put it back in her mouth, but when she got older, she has been able to do it herself.
My 4th is my only one to take a pacifier, and I have been surprised at how much more helpful a pacifier is! She soothes easier at night and sleeps through the night. My others didn't and were much more difficult than she is. I would not take it away at 3-4 months. I don't believe that the need to suck goes away at that age. My older three babies used me as a pacifier through the night up until they were close to (or even past) a year old.
Since I have so many now (baby #5 was born two weeks ago), I NEED to make sure I get as much sleep as I can, and a pacifier is a huge help for my 15 month old (haven't used it for my 2 week old...won't until she's older).
Anyway, so for us, definitely the paci - use a clip to clip it on him, and I would use it until he is considerably older because mine have all needed to suck until they were way older than 3-4 months.
Good luck!