We have found that the Poly, specifically the buildings on the TTC side, has the most convenient transportation. For example, the last 2 times we stayed there we were on the concierge level and those stays were in the Hawaii and Tahiti buidings. It was VERY easy to walk over to the TTC to catch the direct Epcot monorail, instead of having to transfer from the resort monorail to the Epcot one. So essentially (to quote Selinger) the Poly is the only resort to be directly connected to 2 parks by monorail.
Having said that I also have to comment on concierge. We haved enjoyed our stays at Poly conc. I know some have been less than impressed, and the truth of it is we had one incidence of poor service from a CM there. BUT it did not ruin our stay or prevent us from wanting to return. We did think it was worth the money (we stayed on an AP rate and then the FTP) and the food was great, so convenient for the drinks.
I have to advocate taking the "book everything separately" route as opposed to the packages. I just think it is more cost effective. Although we did take advantage of the FTP, that was a GREAT deal. The Visa package is not a very good deal. Look over mousesavers and determine what the prices for room-only and hopper tix are and compare to the package rates. Also make sure what type of tix you need. Don't buy UPHs if you are not going to water parks, DQ, PI, etc.
I would also look into the Swan/Dolphin, true deluxe resorts that offer some really good rates and direct transport to Epcot and the Studios. That could really lower your costs!