I just cut my 870 to 12.5" and it feels like normal length, like how it should feel. It by no means felt 'short'. Now, I'm not much of a shotgun guy and I've become accustomed to SBRs but I can't imagine what a 18" police gun feels like.

I then grabbed my 28" 1100 and dang that was ridiculous.

I feel like it was a much more significant change than going from a 16" AR to a 10.5" AR.

Anyone else feel the same?

All I own as SBS shotguns, so a regular one would probably feel like a phone pole to me now.

I can relate on the rifle side though... I typically only shoot my SBRs and a week ago I drug out my 20" AR and that thing felt like it was a mile long.

Yep.  I bought a Mossberg 590 with a 14", as I didn't have a SBS, and was amazed how much handier it was compared to an 18" shotgun.

Seems like a 14" or so is the way to go - you still have 5 shots in the tube plus one in the chamber, and you gain the handling advantage with the shorty barrrel.