Get what you want.
I'm all for a good shotgun.
I've got an 18.5" Mossberg 590A1 with ghost ring sights.
I've used the 20" Mossberg 590A1 guns with bead and with ghost ring sights.
I own and tried a Remington Tac-14, with pistol grip and with a brace. I didn't like it and converted the Tac-14 to a short barrel shotgun (aka SBS) and put a full stock on it. I've switched back & forth between a pistol-gripped full stock and a straight-stock. Right now, I prefer the straight stock. I also put a barrel with rifle-sights on it rather than having just the bead which is another personal preference of mine.
I've got other 18.5" shotguns with straight stocks, too.
I'd really like to have a 14" 590A1 as I used to be issued:
https://www.mossberg.com/590a1-class...hot-51689.html
but it'd be ~$1000, some paperwork, and waiting for the ATF to approve, which I'd rather not bother with right now.
I agree, the big question is 18.5" vs. 14" (and any required paperwork +$200 w/fingerprints, if going the SBS route); I don't care for the bird's head pistol grips much.