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.
Age of Empires II: Definitive Edition is the harder of the two for you, by 1.7 points. The gap is widest on strategy, where Age of Empires II: Definitive Edition asks considerably more than Outer Wilds. If you want the gentler run, start with Outer Wilds.
Axis by axis, biggest gap first
OUTER WILDS
The only thing gating progress is knowledge inside your own head, which makes it unspoilable once and unplayable if you look it up.
You will lose sometimes. You will not mind.
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.