I would prefer not to have to take the bus everywhere we go as we like to park-hop.
Going via bus has little to do with park hopping per say.
AS the other poster said Poly is on monorail to MK and essentially to Epcot as well. The monorail ride to Epcot is not especially short, nor is Poly very close to anything else but MK.
Also, if you are hopping BETWEEN parks directly, then it almost doesn't matter which resort you stay at. The transportation BETWEEN parks will be the same! Anyone can use the MK to Epcot monorail, or the boat between MGM and Epcot. Any other park to park transfer is via bus.
If you are going back to your resort between hops, then the best resort will depend on which park you are hopping to/from.
Epcot Deluxe resorts are between MGM and Epcot- so you can walk or take boat to either park for any of them and they all balance out- just like the Swan/Dolphin.
BUT
At any of these you'll have to take a bus to any other destination.
the Epcot resorts are most centrally located - but the busing they do use is shared - with the Swan. Poly shares busing with GF, WL.
TWo of the best reosrts for transportation IMO are AKL and Pop - at least in terms of speed. They both use only buses, but the buses are dedicated and only make one stop. The only time getting to Pop is bad is at park close. If speed is your concern - one of these would not be bad. If traveling by method other than bus is your main priority - see above.
Transportation is kind of a toss up. It depends where you want to go and when. The only thing I'd say overall, is that the transportation to/from the mods is the SLOWEST and almost all via bus (except POR/POFQ to DTD).