I'll address the timeshare side of the debate here - I own 6 Marriott and belong to 2 DC's and also have seen both sides:
1. Size - I'm an empty nester and seldom need 2 bdrm suites -- a 5 bdrm house would be totally wasted for me. This is a real DC negative for me but it might not be for you depending on your family needs.
2. Consistent Quality - I have not idea where Bourne got those crazy stats on timeshare use if you own more than 3 weeks a year. I own 10 weeks if you count the split lockoffs and every year take 4 weeks in a row in Fort Lauderdale from Presidents week well into March breaks because it's a snowbird thing for me, getting away from winter. I've done it for 20 years or more...like a second home. The most consistent quality is Marriott IMO ... I've seen the others and know what Bourne means. However the 2 DC's I stayed at so far this year were no better than any timeshare I've stayed in (other than wasted space) -- they had broken furniture and appliances that didn't work and one took 3 days to fix as they didn't have any on-site maintenance. And I still had to make my own beds and clean up, just like in a timeshare, unless I paid extra.
3. Availability - Try to book President's week every year in any DC and you'll see you can't ... not allowed! And that's considered a 'holiday' week, as is all of March, so once you've got that 'holiday' time it's not available to you for a few years...
but you only have a shot at it if you pay more for a higher level tier. Ouch. Yet, I can book President's week to mid March in Fort Lauderdale 13 months ahead and NEVER ever missed getting them...same with a couple of July 4th weeks in Williamsburg. It also means, I've got plenty of time to arrange to book and use frequent flyer miles and get the flights I want 330 days ahead. My experience is that getting a DC in prime time is more difficult than getting a Marriott TS as the DC may only have ONE property in the area you want and there's a mad midnight scramble to be the only one to get that one before all the other members ... and if you lose the race it's too late for the next location. So the mad booking scramble isn't any better with DC's -- IMO it's actually easier with Marriott booking 13 months ahead where they've got some 300 availabilities instead of just one.
4. Service - You get daily maid service, private chef, baby sitting, etc. at any timeshare if you are prepared to pay for them ... and you have to pay for them with most DC's too -- unless it's already included in the annual fees. The timeshare concierge will arrange them for you...but there's no free lunch for such services at DC's either.
5. Responsiveness - My experience is Marriott and I've never had a problem with them ... but I have had problems at one of my timeshares with the Home Owners Assoc who are owners making decisions for other ownes and constantly fighting with Marriott over keeping their standards.
6. Price - You can buy two 2-bdrm lockoff suites that can split into two full 1 bdrm suites at Grande Lakes Orlando Marriott for about $63,000 and get a residual value and 2 million Marriott points that would be $58,000 of that total ... but have a look at the trips you could take with 2 million MR points and your timeshare was free. See this post for more into:
http://www.tugbbs.com/forums/showpost.php?p=561412&postcount=33
My dues for 10 weeks of Marriott timesharing was $5450 last year - I don't know what the dues would be for 70 nights of DC dues! Plus, even with HCC you'll pay more than the cost of buying and owning the suites mentioned in the link above just for the membership fee and own nothing. There's nothing wrong in buying from the developer IF you plan on using the Marriott Reward points program to maximize your purchases by choosing from 2500 Marriotts around the world and flying there business class on those 2 million points! On the other hand, it seems DC's like members who do not use all the allotted time they've paid for as it makes it easier for other members to book their time...but with timeshares you can trade them for points, trade them, rent them, give them to friends when you're not there, or sell them. Very different beasts.
There are many ways to have enjoyable vacations, and you need to assess your past present and future holiday needs before you do anything. DC's are great for some but so are Timeshares. Marriott sold 300 of those above mentioned timeshares in one week! HCC took 5 years to sell that many memberships...and there are plenty who have sold many many less than that.
Brian