Some rooms at the Poly may be less, but there are some differences:
~Separate Longhouses which means getting wet when it's raining.
~No walkway to the MK, but you can walk to TTC to get to Epcot.
~No guaranteed balcony or unobstructed view, like in the Tower. Longhouses are more like GW.
~No commanding views like you have in the Tower.
~No health club within the resort.
~No hot tubs.
~The CR pool area/beach has always felt less crowded to me than Poly's.
I'm not trying to talk you out of the Poly or a split, just mentioning some differences
From the furthest part of the GW compared with being in the Tower, maybe 2-3 minutes walking at a leisurely pace.