If stats mattered that much then Cesar would be the best GK for Brazil and Fabio is only 2cm taller than Cesar so not that much difference.
You seem to be contradicting yourself a bit as well

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all the Brazilian keepers in the game are crap, it's just that Fabio, Cesar, and Helton are the top 3 of a seriously bad bunch of keepers.
Now when you have dog turd to choose from, those 3 are decent. But nowhere near as good as other keepers in the game.
Fabio is amazing for dealing with outside the box shots, corners and free kicks.
Cesar is amazing for dealing with close up shots and that seems to be it.
Never tried Helton but ive played against him and he was just slightly worse than Fabio in my eyes.
So if your good at defending Fabio would be the best keeper, if your crap at defending, Cesar or Helton. But seriously all 3 of them are turd compared with other keepers in the game, but if you want a Brazil team, what's all you have to choose from really.
Height makes a huge difference to keepers, the reason why 83 Hart can pull of some ridiculous saves, but Cech and Stek are a lot better than him because they have a higher OVR and the same height (Stek is 1 inch taller).
Casillas is so good because of his stats.
OVR matters for a keeper as well as height.
I found Cesar to be crap when i used him because im good at defending, therefore i prefer Fabio in a Brazil team, Cesar though is much better if your let the opposing player into your box constantly.
So for Brazil i rate them as
Fabio > Helton > Cesar > everyone else
For Serie A i rate them as
Stek > Buffon > De Sanctis > everyone else
Serie A has a lot more talent keeping wise, than Brazil does, so if your building a Brazil team take a look at Cesar if your crap at defending, if your building a Serie A team, stay away. But he is one of the top 3 of a seriously bad bunch of brazilian keepers due to his stats.
Casillas is the only keeper under 6'2 that is worth buying imo, because his stats make up for the height. Cesar's stats are too crap to make up for the height in the same way but they still make him good for dealing with some types of ****, but he is awful for corner's, i brought him out once for a corner the ball was 5 yards away from him, and some midget managed to out jump his hand, he then fumbled another attempt and mistimed another.
Therefore small keepers are crap for defending corners if you like bringing the keeper out.
Height and Stats both matter, but it does also depend on which Stats are good and how good they are compared to the height of the player.
so if your talking about just brazilian keepers then Cesar is good, if your talking about all keepers in the game, then he is crap, it does depend on what your looking at.
They seriously do need to bring out an IF brazilian keeper.