You definitely close sooner with a direct purchase. Our resale took 7.5 weeks from offer to the ability to make reservations. Usual timeframe is 6-8 weeks.
Financing was just as easy resale as it was direct (we explored both options), with the reseller's preferred lender. Interest rates on a shorter-term loan were 1% lower than WDW's, as well. As previous poster said, you should also explore other options such as home equity loans, that have better rates than timeshare loans.
Closing costs are about $200-300 cheaper through WDW, so add $1-2/pt depending on contract.
Cheaper definitely depends on the specific contract and resort. We figured that we saved about 2K on our BWV contract, after adjusting for the $200 diff in closing costs. If you account for the extra points we got ("loaded" contract), it is probably adds an extra 2K in opportunity cost.
I think the main reason to do direct is the need to be in the system quickly, i.e. to either make reservations or to switch an existing trip to points.