What is the best 40 HST round ?

I haven’t seen any test to indicate one HST over another. In fact, about any 40S&W hollow point is a safe bet. I do often prefer 180 gr over other weights because it has better handling characteristics

I prefer 180.

I don't shoot .40S&W, but I was at the indoor range last night and saw that the guy in the adjacent lane was shooting a G27.  Remembering your question, I asked him what his SD ammo preference was and he said 180gr HST.  I asked him why and he said, "Cause I bought a shit ton without trying anything else, and so I gotta love 'em, or I'm out a shit ton of money".  LOL.  Sorry, I know that doesn't help you, but I thought it was funny enough to mention.

My nightstand M&P40(mid-size) is stacked with the 180 grain HST's. I've been shooting/carrying with the 180HST's for years. This loading is also specifically listed on the official "Best Choices for Self Defense" list here on ARFcom.

I like 180 grain pills the best because they recoil quite a bit less than lighter offerings. I like shooting heavy for caliber loads the best for all defensive pistols due to their usual deeper penetration too. If you are carrying a sub-compact such as a G27 (I did everyday for 5 years), I wouldn't shoot any ammo that was less than 180 grain due to it's recoil. The 155 grain Gold Dot HP's literally felt like I was shooting full house 10mm ammo. The 165 grain was only marginally softer with just as much muzzle flip. I switched to an M&P40c and filled it with 180HST's and carried that for the last 5 years until I switched back to 9mm in a CZ P-01. Both are solid carry guns & calibers...YMMV...

The 180gr HST seems to be the best overall performer.

180s all day if I'm stuck with .40.

I run 165's due to more speed and ftlbs.

Whatever your more accurate with. It won't make a difference. Hope you never need to find out.

I go off numbers and reviews. Then buy a box see how it shoots, do a mag dump, and if it like it, I buy another box for carry.

I prefer the lighter weights (155 or 165gr) in most .40 SD ammo

180 Grain HST for me.

More comfortable to shoot and more momentum behind the bullet to penetrate barriers and crush bone.

155s are in all my .40s.....