I currently use Sibelius 8, VEPro 5, VIPro 2 and most of the VSL full libraries.
I understand using sequencers such as Cubase, Logic, Pro Tools, DP etc. have much better (understatement) and efficient ways to work with MIDI data compared to Sibelius.
However, what exactly can the above listed sequencers do concerning MIDI editing that Sibelius CANNOT do (no matter how cumbersome it may be in Sibelius) - baring in mind I only use VSL libraries with VIPro and all its wonderful humanization features. I also make my own natural tempo maps in Sibelius and often use the 'live' settings (dynamics/timings). I also enter midi controllerdata using 'overdub' in Sibelius for each instrument.
Regards to all and look forward to your direction.