We bought where we wanted to stay, which is SSR (in 2003) and AKV (in 2007). So far we’ve stayed at SSR 14 times (mostly 1BR, but also 2BR and Grand Villas with family), and AKV six times, including three times in Club Level. We have also stayed at BWV six times (four of them during F&WF), BCV twice (both during F&WF) as well as BLT, BRV, CCV… We’ve never had a problem getting in somewhere other than our home resort when we’ve wanted to, but we almost always stay in 1BR villas which are easier to get, and are flexible in terms of when we can travel. Our next trip is in April, when we’ll be doing a split stay between SSR and BWV. We’re going again in September (for F&WF), and we’ll be staying in AKV and BCV.
My advice would really be to buy where you want to stay if location is very important to you. If you always want to stay at the Poly, it would make little sense to buy somewhere else only to find that you can’t get into the only resort you really want when you want it. If you’re flexible it may make more sense to get a more cost effective option.
Not sure if that helps, but it’s my two cents anyway.