I see where you’re coming but I think the greatest in your list have something more than the strongest. They are all close but the greatest have the little something that made them greater and also stronger.
I wouldn't say Stronger, i believe a Fight between them would end up like Dorry & Brogy
Two men trying to prove who is Stronger but unable to
However Greatest Group definitely have something more that Group of Strongest which makes them Special
I believe those Greatest have Potential & Uniqueness that allows them to Defeat Opponents that the other Group might lose against
But between each other, they are equals
For example, i believe Shanks fares against DF Users better than Mihawk because i believe his CoC is more Advanced than Mihawk's but i believe Mihawk holds much more Power than Shanks thanks to his Black Blade & Swordsmanship just like WB had Gura Gura No Mi & can tilt the world, something that Roger can't do & just like Sengoku have a DF & also Kaido is more monstrous than BM ... etc
So Greatest = Strongest
But Strongest > Greatest when it comes to Power/Ability
While Greatest > Strongest when it comes to Effectiveness/Potential