I don't want to post the RMAA result directly because they can be misleading for those who like to jump to conclusion using graph and don't understand RMAA limitation as a tool, especially the fact that you can't compare RMAA measured on different run / PC / gears.
Anyway, these are the result between two Lightning-to-30pins adapters (genuine, directly from Apple) and the headphone-out (match to line-level voltage).

From left: Lightning adapter cable version, Lightning adapter dock version and headphone-out
Note, you can't see the multitone FR because this measurement was done on an old version of RMAA and those result don't display on the new RMAA version I just installed. However, all three show the same flat 20Hz to 20kHz just so you know (as you can see on the swept sine result)
As you can see, the only significant difference is on the crosstalk and headphone-out is actually better.