We went through the same thought process and this is what we found.
We bought our first 150 contract for VWL from Resale and it went very smoothly and the cost pp, even with the closing costs was considerably less than what Disney would have charged. Take a look at the ROFR post and you will see what the resale prices are.
Then we wanted to add 40 points at BCV and were put on a wait list through Disney for Aug UY we waited from Feb til last week and still no call. Disney will not let you buy time outside your UY. The pp through Disney was I believe $95 or $104, I am not sure because we made our request before 6/1. Anyway, we bought through resale and paid $97 and will pay closing costs. This is ok with us because we wanted to add my mom to this contract and did not want to wait for Aug UY, any UY was fine with us.
Long story short, if you are buy 160 or more, you definately could get points cheaper even including the closing costs, through resale.
If you want less than 160 points, you have to go through resale, since Disney requires a minimum 160 points.
If you want to add on a few points and already have 160, it depends on the resort you want to purchase at. For instance, I have seen small contracts at OKW to be lower in PP from resale than Disney.
There is a lot more to consider when buying resale and the pp, as well as other things to consider, like the dreaded ROFR
After going through it 2 times, I could write a 3 page post on that, and I am sure others would too. There are a number of previous posts about resale vs Disney. Use your search feature and look for it and I think you will find all your answers there.