When you stay onsite, where do you stay? What time of year? For how long, on most trips? Is it affordable for you?
If you tend to stay at the "values" then DVC will likely cost more.
If you go during prime holidays (Christmas/Easter), DVC may or may not cost more.
If you prefer long weekends rather than full weeks or weekdays, DVC may cost you more.
If you would finance most of the purchase, DVC may cost you more, due to the interest you'd pay over the loan period.
IF you tend to stay at the nicer Disney hotels and condos...
IF you avoid prime holidays (very high points)...
IF you like full week stays or perhaps more weeknights...
IF you can afford to pay for most of it without taking out a loan...
THEN it sounds like your frequent onsite stays at Disney may make you a very good candidate for DVC.
If you'd think you'll like to stay for mostly full weeks, if you like OKW and SSR, if you'd avoid most major holidays, THEN you may want to consider another avenue, trading into DVC from other timeshares and save some money. But this is far less flexible.
Lastly, if you plan to use points regularly to trade out, you may want to rethink the size of the DVC contract that would suit you. Buying DVC points as a trader is an expensive way to enjoy trading into II.

Buying DVC points to use nearly all of them (through banking and borrowing) to stay at DVC resorts is a good idea.
