You have to really ask yourself how much damage HAM is going to soak up over your career. Let's say that you're a melee combatant that is often the target of attacks.Now, let's assume the average number of combat rounds per encounter is 3.5 (I'm just pulling numbers out of my head, no arguments please!). And that you're attacked in each of these turns.
Then we assume you actually have 6.5 combats on average per session, and your DM uses milestones so you level every 3.5 sessions. This means that by level 10, you will have been attacked 796.25 times.
Now, if 40% of those attacks are hits, that's 318.5 attacks that deal damage. Which means that HAM by itself, has potentially reduced your taken damage by 955.5, very close to a thousand points of damage.
By the same token, that extra 2 points of Con, giving you 10 more hit points by this point, has probably mattered only a fraction of an attack per combat. Let's say about half at 10th level (looking at a random CR 10, the Stone Golem, who does 19 damage on average per hit).
So that's one half of one attack per combat, of which we've determined you've engaged in roughly 205 of by the time you're level 10. This is also a pretty big number, but it comes at a cost; you need to recover those hit points each battle.
What that cost is, depends on your class. A Short rest and a Hit Die or use of something like Second Wind? A spell slot from a caster? A Healing potion? A use of a healer's kit via the Healer Feat?
The resource allocation might seem trivial for your party, or quite large; it really depends on your playstyle. If your DM is little stingy on money, or likes to run you ragged every session, I think HAM gets a lot better. If they aren't strict about number of encounters, only have a few set piece combats, and give out standard loot, then go with the Con (which has the nice side benefit of increasing Con saves and checks).
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