everything dogg said is completely accurate conclusions wise, as far as your questions go, but i do want to kinda clarify one item. in the zone all 5 defenders are averaged for every shot.
the difference is what formula those players' abilities are calculated with, on the defensive side of things. as he said, in a 2-3, there are 3 equations used, a pg-sg equation, a sf-pf equation, and a c equation. the C equation in the 2-3 relies heavily on block - so heavily that i question if it actually surpasses defense in importance? which would generally be an exception because there's virtually no scenario in HD where defense is not the #1 defensive attribute. i'm not saying blk for the 2-3 c is the most important - just that its close enough, that i question it.
in the 3-2 there's a pg-sg-sf equation which basically treats them all as guards, and a pf-c equation which is more big-like than the sf-pf equation in the 2-3, but i don't think it goes as far as the C equation in the 2-3, which feels sort of like a unique artifact to me.
but i also am not very good with zone... its the only set i don't have multiple titles with, and i don't have much intention of ever changing that. so i can't really give a nuanced view of things like i can with most other setups. still, to your question - your two listed guys in the 2-3 - i think its a no-brainer to go with the reb/blk guy. i hate playing that low of ath players in general, but rebounding is up there with ath on its own (ath > reb for scorers, for non-scorers, reb >= ath, generally speaking. not always). so with it being a 2-3 center i think its an easy choice.
i will say though - open yourself to the 3-2. the 2-3 tends to be better for not as good teams, but 3-2 becomes very competitive for the better teams. on my best zone teams i tend to run mostly 3-2. the reality of zone teams is a lot of times, the players dictate which you should play. its great when you have a sweet SF in zone and can freely switch, sweet well rounded SFs in zone can be huge. there is no better 3pt defense than the 3-2, and its really not close. the 2-3 is also the best 2pt defense. you give up rebounding and turnovers, which makes zone probably the hardest set to win championships with (piman has had some great zone teams, i would go find those and study them). you don't have to do this now, but if you really want to be a great zone coach, eventually you'll need to work the 3-2 into your arsenal - i think, anyway.