Why a shotgun
Ok, so lets step back and ask a few questions-
1) What is the purpose for this shotgun (i.e. hunting, home defense, truck gun, etc.)?
2) Who will be using it (i.e. a 250 lb man, 100 lb woman, 10 year old child, all of the above, etc.)?
For hunting, I would look at my local laws and regulations concerning shotgun use while hunting. For home defense, I would agree that a good pump is probably your best bet. 12 or 20 guage will both perfom well for HD, so think about who will be shooting your weapon before you pick. I have a 20 ga Rem 870 youth model that I keep by my bed- 4+1 shells of 7 1/2 will still put a 1 1/2 inch wound in a person at 21 yards (based on my range trip) with each shot. I picked the 870 because it came with the 21 in barrel, and the light weight makes it easy to move through my home if needed.
As to your first experience, you mentioned a pistol grip shotgun. Was this a pistol grip only, or a pistol grip with a shoulder stock. If it didn't have a shoulder stock, try one with a shoulder stock and see if its a little more comfortable. A 12 ga has a kick that def takes some getting used to (and part of the reason I picked a 20 ga for HD)...