Someone who bought resale can probably give you more detail on the benefits of resale ,but I will tell you why I bought SSR.
As you notice on these boards everyone says over and over again "buy where you want to stay". That really was first and foremost for me.
I really, really like DTD and PI and look forward to being relatively close at SSR. I also like the fact that the spa will be next door. Those are things that appeal to me, but they may not mean anything to you.
Many people here LOVE the
DVC properties in the Boardwalk area. I'm just sort of lukewarm on Boardwalk so this was not a plus for me. Those properties are great though for being able to walk to Epcot. OKW has the larger rooms, close parking and relaxed atmosphere. VWL is also a favorite with many for its lovely atmosphere.
Once you decide on where you want to stay - well then it pretty much comes down to SSR or resale. You can wait list for the sold out properties or buy resale from a broker or maybe directly from an individual.
I still feel that the most important factor is buying where you want to stay. That being said - the process of buying a new property from Disney (I can't speak for the Disney resales) was SO EASY. I literally made a phone call, gave my cc number (I'm getting lots of Disney Dream Dollars for this) and signed some papers that they sent me. No waiting for right of first refusal, etc - but I am having to wait for SSR to be completed.
I've heard that the financing is easier and cheaper through Disney but I do not have first hand knowledge of this.
I forgot to mention the added length of the contract but that was not a real issue for me as I am old! and do not have children.
Hope this helps.