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 0.7 points. The gap is widest on strategy, where Age of Empires II: Definitive Edition asks considerably more than Castlevania: Symphony of the Night. If you want the gentler run, start with Castlevania: Symphony of the Night.
Axis by axis, biggest gap first
CASTLEVANIA: SYMPHONY OF THE NIGHT
Straightforward once you find the right weapon, and famously obtuse about its second half — the difficulty is knowing that half exists at all.
Real resistance. Expect to work for it.
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.