Compare weapon base damage
Check attack speed
Check critical strike chance
Check damage multipliers from armor, accessories, buffs, and class bonuses
Check weapon use time and DPS
Test against the same target with the same setup
Compare damage per hit and total damage over time
Use the in-game damage numbers or combat log if available
Account for defense, resistance, and debuffs on the target
Compare summon, minion, sentry, and projectile damage separately if relevant
Use the same difficulty, mode, and modifiers for both setups