You've taken a solid research approach, and I applaud you for that. The one thing I couldn't tell from your post was whether you had yet shot the 30SF and the 38 side by side.
You hand may be way bigger than mine, but with the 10-round mag, the 30 and 30SF give me a full three-finger hold (not counting trigger finger, of course) unless I'm wearing heavy gloves. For me, the 30 with that mag and the 19/23/32/38 Glocks don't feel a whole lot different except for trigger reach, which is a bit greater in the .45 ACP gun.
There seems to be virtually no real difference between standard pressure .45 ACP and the .45 GAP. The .45 ACP +P does give you more smack, but that's happening on both ends of the gun.
Shootin' em side by side will be like getting acquainted with two slightly different puppies of the same breed. You're gonna bond with one or the other, and unless there are logistical reasons (or round count reasons) to go with one over the other, that bonding will probably decide it for ya right there.
Let us know what you finally decide, and what tips the balance of your decision...and thank you for your long police service!