If you are going with all girls, I don't think it matters much. My general approach is - no drakes larger than ducks. This may sound extreme, but if one is new to ducks, and wants to avoid heartache and injury, that is one way to help. Drakes can be brutal. Big drakes can accidentally cause harm, just from the size difference.
There are always exceptions to the rule, but the Duck Forum has seen a number of stories of problems with drakes. So if you are not prepared to have a separate area for a drake, then go with smaller drakes. Another way to say this is, a Pekin female may be just fine, especially if you get them all at the same time.
If you have analysis paralysis, then flip a coin! Ducks are wonderful!