the controller deals well with larger sizes, basically it has enough channels and other stuff
its cheaper
it comes with the new NGFF, which means, cheaper storage for macs, since this is not a proprietary connector, it can reduce bulk costs, because its not only apple that will buy that
Also if they change the connector it opens us to avoid SF or the extremely expensive samsung 830 specially made for macs as an upgrade
and to top that off, we are waiting to see the new intel SSDs, hopefully using the SC3700 controller in the new format
aside that it allows them to move out from the dependency of samsung parts
its a real beneficial move