The rebounding disadvantage is significant for zone, especially the 3-2. Among starters, I’d say you were at a disadvantage anyway, position by position. You had some slight rebound attribute advantages in the frontcourt, but you were at an athletic disadvantage.
I default to -2 when using 3-2 as a base. Against a normal, balanced offense that shoots what I consider a normal amount of threes and gets a normal amount of scoring from guards, I play -2. That’s for rebounding purposes more than preventing inside scoring. I move to -3 and -4 pretty fast, if they have big rebounding advantages.