Co-pilot MFD
I have three screens - 5600T : 5500T : 5600T. Both 5600s show EFIS & eng & the 5500 shows map & plates .. The MFD 5600T is backup in the event the primary is lost .. It, also, is useful with a Pilot in the second seat .. I have the 650, ARINC, A/P, & xpndr wired into the pilot 5600.
I shoot approaches relying on the PFD for guidance & 5500T for situational awareness. The second 5600T is backup & well within field-of-vision.
Frankly I would wire the A/P & xpndr into the 5500T for flexibility & to allow the option of set-up chgs in the 5600 without taking the transponder & a/p off-line.
The config gives me fault tolerance & a cross check capability.