[JMason]

As an anecdote, I ran a GURPS conversion of a D&D adventure I had previously played in D&D 5th edition. What struck me, after reflecting on how each games went, was how many of the combats played out very similarly. The only difference was that in D&D, it was "hit, damage, miss, hit, damage...." and in GURPS it was, "attack, defend, attack, defend, attack, hit, damage...".

This really hammered home the idea that D&D HP was really just a timescale for the battle, and reflected skill, luck, etc., not physical damage.

The real difference IMO, was that GURPS combat was more exciting. It didn't happen often, but there was always that chance that a lucky blow would end the combat early. This was way more interesting than just hammering on piles of HP, turn after turn. So, I am hesitant to ever add tons of HP to enemies.