Ali's best weight wasn't 220 lbs. At 220 or more, he was out of shape.
Neither 190 lbs 'cept at maybe 19 years old.

A prime Muhammad Ali was 212 lbs at 6'2½".
A prime Marciano was anywhere between 184 and 189 lbs at 5'10¾".

Marciano trained himself down to a supremely conditioned 185, but this burly guy was naturally well over 200 lbs. 45 year old Marciano dropped 50 lbs for that computer simulation bout with Ali in 1969.

Heavyweights trained off the fat back then because they had to be prepared to go 15 rds, and they wanted the speed and endurance. Many current Heavyweights are carrying way too much fat.

Both had terrific chins.
Marciano had a much harder punch, Ali was faster.
Marciano bled, I believe Ali was only cut once in his career, against light-Heavyweight Champ Bob Foster.
In their primes, both had incredible stamina and endurance.

Concerning weight and size:
5'11", 205 lb Frazier gave Ali hell, and even defeated him the 1st fight.
185 lb Henry Cooper knocked down Ali with a hellacious left hook.
Some thought 188 lb Doug Jones should have got the decision over Ali.
191 lb Sonny Banks knocked down Ali also with a left hook.

Some of these smaller guys gave Ali more trouble than Foreman and Liston did.

Marciano should never be discounted nor his abilities disrespected; he was a Great fighter.