It depends on the resort you want, the number of points you are looking to buy, etc.
When buying resale, you are not restricted to buying in with a minimum # of points. Through Disney, it is 160.
The newer resorts are available primarily through Disney. While you may find a few contracts for BLT right now on the resale market, it will be cheaper and easier to just buy direct through Disney (ie: with a 200 point contract, you can get it for $96.00 per point--providing you have a member referral).
Some of the resorts are much cheaper through resale. Right now, SSR seems to be the best deal out there as you can get it around $68 - $75 per point, it doesn't expire until 2054 and the MF's are fairly low.
Of course, most will tell you that you should buy where you want to stay. Owners get a to book reservations at their home resort 11 months in advance. At 7 months, reservations open up for all owners at all the resorts. Many owners book a room at their home resort at the 11 month mark and then call at 7 months to change resorts if they want. If it is available, they are able to. If not, then they end up at their home resort. That is why you want to be happy with your resort.
If you can't make reservations more than 7 months in advance, then home resort is not really important and buying a resale contract to save money is the best bet!
I have used the Time Share Store and they are wonderful. I have also heard great things about all the others--although I believe that GMAC has the highest costs. But I have heard that owners who used them just took that into consideration when making an offer.
Good luck!!