i'd wait until they become root bound. they're easier to handle and the rootball usually stays in place during the move if slight compaction has occurred. you'll know when it's time when you start seeing the hair-like roots growing out of the drain holes...

i start seeds in the pots they'll be growing in for the 1st 6 weeks or so...or until sexed then take females and transplant them into 5 gal pots for the duration of the grow (unless they're to become mother plants)