I'm not a ballistics expert. I see the same reviews you probably saw. I have fired both P9HST1 (124gr) and P9HST2 (147gr) from three platforms, S&W M&P Shield (3.1 inch barrel), S&W M&P Full Size (4.25 inch barrel) and my home built AR-9 SBR (4.5 inch barrel). From a felt recoil perspective I have a hard time telling the difference. If anything it seems that P9HST2 feels just a bit lighter which is opposite from what you were thinking.
From all the reviews, it seems like HST bullets expand reliably even at lower velocities than specified in ballistic gel (including through 4 layers of denim). I think this is really good for short barrel weapons (less than 3.5 inches). It seems that P9HST1 does not expand as big as P9HST2 but penetrates a little deeper. I personally think penetration is important as long as it doesn't over penetrate. So for my Shield, my carry ammo is P9HST1. I would not feel uncomfortable carrying P9HST2 either. The reason I buy P9HST2 is because my SBR will be suppressed so I want to have subsonic ammo in a personal/home defense weapon. P9HST2 is pretty hard to find at reasonable prices so I don't keep a lot on hand, but I do keep a decent supply of the P9HST1 (700 - 1000 rounds) on hand.
Either appears to be very effective based on the tests, so I would not worry about which one you carry. Good shot placement is the key factor, and both shoots pretty much the same at short self-defense distances. To me, I really don't see or feel a difference in shooting dynamics. This is just my personal opinion. Like I said, I am no expert.