Is one method better than the other?
Not necessarily. But you need to make that determination. Do you want to buy-in with 160 points which is minimum required by Disney if you direct purchase with them ?
or
is a contract with less points better for your situation ? Then purchase via resale market. Also, if you do purchase resale, no matter the amount of points in your contract, your membership will not be treated any differently so no worries there.
If you find you'd like to own more points in the future, either at your Home Resort or even want points at another DVC resort, you can purchase add-on points directly through Disney at minimum of 25 points with cash or 50 points if financing and you also have the option of adding additional points by purchasing another resale contract.
Use Points Chart link at upper right corner of page to calculate number of points you'd need based on
resort/size villa you'd need/ # of nights in typical trip/season(s) most likely to travel
- -note that if you plan to make trips every other year or every third year you can purchase half or third this amount of points because with banking &/or borrowing you'd have enough to do so.
Does Disney limit the availability of certain resorts?
Disney has all DVC resorts available to purchase but their focus will be to get you to purchase at the resorts they are currently marketing which are BLT, AKV, SSR and VGC at Disneyland - - you may have to be waitlisted a bit to purchase points at earlier DVC resorts such as OKW, BWV, BCV, VWL, & offsites HHI & VB, but they can sell you points where ever you want to purchase. These earlier resorts are usually readily available on resale market but also know that AKV & SSR contracts show up in healthy numbers on resale too and BLT contracts have also begun to turn up on resale recently.
The resort you buy into is known as your "Home Resort" and you will have a 4 month booking advantage at your Home Resort over DVC members who do not own points at that resort - you may book at your Home Resort from 11 months through 7months+1 day before check-in day you'd want during your owner's priority booking window; at 7 months or less all DVC owners no matter what resort they own at may book at any DVC resort.
Are the fees different when purchasing different ways?
Resale closing costs/fees tend to run somewhat higher than Disney's but depending upon resort you pick to buy into usually resale prices per point end up saving you quite a bit of $ over Disney's prices so resale's higher closing fees usually are not much of an "issue".
If you purchase through Disney at a resort they are currently marketing there are usually some incentives depending upon resort & amount of points you purchase & also if you have a member referral ( there is 'need a referral thread' here on this board where you can find a member to refer you ) - - sometimes this can be better choice than purchasing resale particularly if you want BLT or AKV for your Home Resort & you plan to purchase around 160 pts anyway it probably makes more $ sense to buy direct through Disney then because of current incentives being offered for these resorts.
It's worth taking the time to do the math to compare both direct purchase prices/incentives to resale prices and see where your best value lies.
If financing, what types of interest rates do you get?
Disney's financing iirc ranges from about 10.75% - 14 plus % depending upon credit-worthiness. There are financing options available too when purchasing resale : this board's sponsor The Timeshare Store (click on their banner at top of page) is an excellent, knowledgeable DVC reseller, myself and many here have purchased through them. The Timeshare Store recommends Tammac Financial for financing.