Myrtle Beach
I think that you are doing all the right things. Take your time and educate yourself.
You might even vacation once in Myrtle Beach before you buy. Many timeshares offer 2-3 free nights if you go on their presentation. Hey, stay at two or three.
In any case, you should go to Myrtle Beach with a list of timeshares to check out.
Myrtle Beach timeshares are in high demand--especially during the spring and summer. One reason is that Myrtle Beach is a one day drive from mid-Atlantic states (Virginia, PA, Del, NJ, and NY.) And there's a lot to do at Myrtle Beach. And it's nice to have your own car and bring as much "stuff" as you want. That's why we bought in Virginia.
The negative is that a lot of the resorts are old. You may want to stay away from them. And some of the newer resorts are not on the water, or have very small rooms. I agree that the Marriott is the best that I'm aware, but it's also a little pricey. Still, if you buy resale, you will save 10's of thousands. Expect to pay over $5K to purchase a Marriott week, and pay about $1K annually in fees.
I also recommend buying a prime week--a week that you would often want to use. I prefer fixed weeks, but make sure you have enough Points if you purchase at a Points resort like the Marriott.
Check out the ratings of timeshares on TUG. Enjoy researching Myrtle Beach.