It is most likely due to a combination of pruning and training/staking, and possibly due to nutrient supply and other environmental issues. If I had to guess, I would say that the two different types came from different growers which would explain a slightly different habit.

Generally vigorous plants show more weeping characteristics than nutrient deprived specimens since the weight of the long new shoots causes the pendulous nature ('Crimson queen' is usually a bit more compact and doesn't show as much of this variability as say 'tamukeyama' IMO). If the two plants were planted in the ground at your house and given the same training and nutrient supply, they would eventually start to mirror each other on the outside.

You will have a large amount of control over what type of outer branching you have after a couple of years under your care. You can't, however, change the interior limb structure very much which is usually the most important part to the trees beauty. This should be the primary factor when choosing between different plants of the same cultivar in my opinion (especially weepers).