I noticed the same thing. Active Sync also outperforms MAPI in syncing a large email account.

The initial synchronization will take some time to complete as we're pulling down a 1:1 copy of the account, but subsequent updates should be very fast. If you're seeing delays after the initial sync I recommend submitting a ticket so we can take a look. As to EAS performance over MAPI, it is expected EAS will be a little quicker as its a mobile-focused sync protocol and isn't syncing nearly as much data down to the client.