Everybody's circumstances will be different. We own OKW and love it there. Our dues this year are about $1400. We buy two AP's and save $213 ($100 each, + tax), which if applied toward the dues leaves less than $1200 in dues. That's $100/month if we want to look at it that way.
We also own Marriott's Shadow Ridge, next to Palm Springs, CA. Taxes are collected separately by California, so we pay dues to Marriott and taxes to CA. They total $875 this year. That's about $73/month. If we want to trade it, we must belong to II. That's about another $6.60/month, and if we trade it out any given year, that adds another $6.60/month trading fee. So owning Marriott currently costs us about $86/month more or less, depending on how we use it.
Our Shadow Ridge is Silver season, and we get 1-week (7-days) in a 2-B/R villa. Depending if we trade or not, that comes out to about $142/night.
We can get almost 10 days straight at OKW in a 2-B/R villa in dream season (similar to our Marriott season) with our points. (Actually 9.5 nights so will use that figure). That equates to about $125/night. So for us owning
DVC is cheaper in dues on a per night basis than our Marriott timeshare.
If we elect to only use our OKW points on weeknights, and only in a 1-B/R, we can get 16.5 nights during Dream season, which then comes out to about $72/night.
But DVC is so flexible. We can save even more by using points in Adventure or Choice season, or spend a little more and go during Magic or Premier seasons. We can go on weekends or not, we can get a Studio and save, or go with a full Grand Villa. Finally, yes, we can stay at other resorts which affects the points required, and thus the total 'cost' of a stay.
The point is, the flexibility adds so much more to the equation.
And yes, Marriott is great also, and does have some flexibility to it. We can't use it year round, but do have a window of several months for our 'silver' season. If we don't ever want to trade and always want to use it as a 2-B/R we don't need to belong to II and would never have any trading fees. But to get more flexibility, we do those things. We can split it up and get 1-week in a 1-B/R and another week in a Studio. (Although another fee applies to do that) However this option certainly affects the 'cost vs. value' equation.
And owning II has additional benefits, such as their getaway program which allows us to book stays at many timeshares for only the cost of the maintenance fees or less, without ever having to own there.
In conclusion, value is in the eye of the beholder. Whichever one is cheaper or more expensive is irrelevant. They both have features unique enough individually, that for us, there is 'value' in owning both.
As for the initial purchase costs, we bought DVC in '93 and got free park passes up to the year 2000. When we bought Marriott, we got thousands of Marriott reward points that we could use for Marriott stays. But overall the free park passes were probably worth more in actual $$'s. But that was a great bonus we received, and was never repeated. Other past or current DVC sales incentives have their own merits. To try to compare purchase incentives between programs probably serves no value.
I can't easily compare the initial purchase prices between the two, since DVC was purchased earlier (1993), but with several add-on purchases a few years later. However, if I were to compare purchases based on a common 'present year' dollar figure, I know DVC was a more expensive purchase than Marriott if I were to compare purchasing exactly 7-days worth of points for mid-season.
However, as far as I'm concerned, it's the 'value' to the purchaser that matters, nothing else.