I certainly think it isn't an easy thing to quantify.
Gamers vs miners damaging cards:
- Fans:
- Miners: Fans will be running constantly for months at a time
- Gamers: Fan will only be running a few hours at a time
- VRM and power circuitry:
- Miners: a constant pull for months at time, but probably heavily undervolted (power costs money both in term of electricity and possible having to use bigger PSUs)
- Gamers: a variable pull for a few hours at time
- GPU silicon and thermal cycles:
- Miners: constant load, few thermal cycles
- Gamers: fluctuating load, lots of thermal cycles.
- Overclocking and underclocking:
- Miners:Usually more likely to underclock, but Ampere and GDRR6X might be overclocked as memory is the more important metrics (at least for ETH)
- Gamers: most would leave it alone, but plenty of overclockers too.
Some of the things miners do will damage a GPU with fans being the most likely point of failure.
Some of the things gamers do will damage a GPU with thermal cycling being the most likely point of failure.
Surprise, surprise, there is no easy simple answer. A mining GPU where the GDDR6X hasn't been damaged would seem like a good candidate for watercooling or aftermarket aircooler. If cheap enough, a few 120mm case fans might do too.