Compared to the 32 hp (16 max+ 16 from HD) from +2 Con or 32HP from toughness...
HAM needs to reduce 11 hits a day to be better (14 at level 20).
An adult blue dragon does 15 damage on a hit. Or 165 damage in 11 hits.
So HAM could be better if your DM only makes weapon attacks and hordes of smaller creatures. But 1 lighting beath for 66 damage and +2 con wins. Plus it doesn't scale like Con does, and you get +1 to Con saves.
At lower level, HAM easily wins, particularly if you can make use of the +1 Str.