As far as I know, Marriott resale prices with points are the same as they are at actively sold resorts. In fact, most resorts have a deed clause that permits Marriott to have first refusal on timeshare sales that they have been taking quite often in recent years...and then resell them at their current prices. So a fantastic deal you find on a Marriott resale might turn out to be a fantastic deal for Marriott to snatch away from you.
I believe in the Marriott Rewards program very much as it has provided my family with many wonderful trips. But those trips happened largely because Marriott used to provide as much as 500,000 points to buy a $18000 week. Only a few Marriott can be traded for points every year, so that means you have to use/trade it every other year. But if the maint/tax bill is too high, as it is in Hawaii and Fort Lauderdale and St. Kitts, it's not an efficient way to buy points...thus not a good benefit, except for emergencies.
There is the fear that the point program could be devaluated much in the same way that hotel and airplane rates go up every year. So far that hasn't happened too often but it's always wise to spend those points on great trips sooner than later - just the same as it is to spend excess cash rather than hoarding it. I'm guessing that the points program is of more value to empty nesters like me than it is for young families and if it looks like it will be a number of years before you can take advantage of the points benefit it might not be the best choice to buy direct due to the fact the number of points you can get each year does not change but the number of points needed for trips will probably change over time.
However, to say that the points program is not a good 'investment' might only be correct if a resale buyer took the money they saved and actually invested it to make money rather than blow it on a car. When I've taken all my points travel, I still own the timeshares.
Study your vacation needs for the points program - present and future - and study
www.marriottrewards.com as well. Then compare the resort prices and annual fees and the points you get. For me, it's a plan where I can get business class seats and stay a week in category 6 or 7 world class hotels which would add up to a tremendous cost if I had to pay that way. If you pass on, your kids inherit your direct-purchased timeshare
and the points program, but it's hard to know if the program will be as good for them as it has been for me. Therein lies the critical problem Marriott faces with the Rewards program for the years ahead. Certainly there is some comfort in the fact Marriott wants to retain their best customers with MR incentives and competition from Starwood and Hilton is fierce.
Brian