Hmm, the only difference I noticed is that MACO engines are a bit slower in sector space (18.39 vs 20.39 for my cruiser).

MACO XI
+8.8 Starship Driver Coil
+14 Flight Speed
+11 Flight Turn Rate
Thrusters: 25% speed when engines are disabled
While in Sector Space Flight Speed set to Warp 12

Borg
+5 Engine Power Setting
+12 Flight Speed
+11 Flight Turn Rate
While in Sector Space Flight Speed set to warp 14.

Well. Tough decision Although if the deflector is really that much better, I may try it as you recommended.

Edit:
"Sorry, I should have been clearer,"
Well, sorry, me too. I don't have the MACO deflector yet. I was so sure you knew