Whether buying DVC or considering renting, what's reasonable depends on your situation. For some it is better to rent, for many others, it's better to buy.
I only know DVC and Marriott well enough to contrast them. Overall I'd say they're very comparable on quality though Marriott has a few lessor properties compared to DVC and is thus more variable from a quality standpoint. DVC works on points and is very user friendly for MOST situations. Most Marriott's are floating weeks and you must reserve a full week with some VERY LIMITED exceptions. Both are expensive and how you actually use it will determine how the costs compare between DVC and Marriott. For a full week's use in a 2 BR at most top resorts DVC is about 30% more expensive and about 30% higher fees on average. If you can take advantage of some of the flexibility such as S-F stays, DVC becomes a fair amount less expensive and actually cheaper than most mid to top end Marriott's. Locations are a big issue, where do you want to go? The other issue is how you'll use it, for trading to other resorts, Marriott is a MUCH better choice in most situations though ANY high end, high demand ownership generally is not a good choice for exchanging if $$$ are part of your equation.
To me it's not an either or. I think one of the best ownership options is a small to mid size DVC contract, an EOY Marriott to use and an appropriate EOY Marriott more oriented for trading. With both EOY being the same EOY orientation (odd or even) as the one you use. The reality is that finding EOY units are tougher, esp at a good price so you'd frequently have to decide whether to buy EY and possibly rent off years for a high end option. Done correctly, this decreases one of the main problems with the Marriott system, that of getting high demand week reservations.
