Gear 4 swatted Kaido around, avoided his attacks, tanked his boro breath directly when he was being attacked by 2 yonko back to back, alone. It got to the point Luffy was able to pummel Kaido and Big Mom couldn't even risk intervening (and bruise Kaido that still had the same bruises in the same places after turning hybrid). It is safe to say G4 is stronger than unawakened Kaido, Kaido can outlast G4, but he can't outperform it.
G4 impressed Kidd so much he pretty much gave up on Kaido and completely freaked out Big Mom until she saw the time limit.
If you want to see why base damage is important after adding the appropriate haki penetration- think of haki bypassing his scales as sort of like Kaido's kryptonite. What would damage Superman more if it hit him- a kryptonite bullet to the chest or a kryptonite tank shell to the chest? The first would create a small hole, the second would explode his torso entirely.