Head to head
Which one will break you first?
Two fingerprints on one grid. Both are scored through your profile, so this answers the question for you rather than for the average player.
Spelunky 2 is the harder of the two for you, by 1.4 points. The gap is widest on punishment, where Spelunky 2 asks considerably more than Age of Empires II: Definitive Edition. If you want the gentler run, start with Age of Empires II: Definitive Edition.
Axis by axis, biggest gap first
SPELUNKY 2
Every death is your own fault and every run is a fresh cave. The systems interact thoroughly enough that it kills you in ways nobody has written down yet.
The game is the antagonist. Good luck.
AGE OF EMPIRES II: DEFINITIVE EDITION
Build orders are the curve, and the campaigns teach almost none of what the game actually asks for. The hard AI does not forget its economy while it fights.
Sustained pressure. Progress is earned.