Lightning
Was always going to be abandoned at some point so the "existing stuff will be obsolete" argument never held much sway with me.
The "We committed to supporting lightning for a decade" argument is much stronger, particularly since they did that with the 30pin connector as well - and in the timeframe of those two Apple specs I must have had more than a dozen crummy connectors from other manufacturers.
How many people use wired data transfer to/from a phone nowadays anyway?