Your GMail will come to your device instantaneously, but your AOL will have a 5 - 15 minute delay. However you can do what I do with my .Mac account:
1. Set your AOL mail account to forward to a Yahoo email account.
2. Set your blackberry to get the Yahoo email (this is instantaneous).
3. Set the reply-to email address for the Yahoo account to your AOL address.
This way you get your AOL email delivered instantly (via Yahoo), but when you reply to those emails it appears to be from your AOL account, so no one ever sees your yahoo email address.
Does that make sense?