Quick update: after spending time fixing and refining the Age Of Empires 4 battle simulator, I’ve now brought the same idea to Age of Empires II DE.
The Age Of Empires 2 version is live now and lets you compare units and test matchups more realistically instead of just looking at raw stats.
I’m still polishing the simulator and checking edge cases, especially around upgrades and unit interactions, but the main version is ready to use.
You can try it here: 
https://aoescout.com/age-of-empires-2-de/compare/units
If you notice a matchup that feels wrong, or there’s a unit interaction I should test, let me know.