The Marriott chain has few hotels in a fair number of European countries that are popular tourist destinations, such as Spain and Italy.

Although I tend to concentrate on one airline award program (American/OneWorld can get me most anywhere I want to go), this is the argument for using two different hotel award programs. If you enjoy international travel, and if you accumulate Marriott Reward points, I think you also need to work on Starwood or Hilton to increase your options.

This is also an Achilles heel in the Marriott timeshare program. If you buy a timeshare from Marriott, you have the option of converting your timeshare usage to Marriott Reward points every other year. Marriott sells this by telling you that you can then use your Reward points for international travel. And that is definitely true for some European cities, such as London and Paris (where there are numerous Marriott properties). But your Marriott points won't help you much in Spain or many parts of Italy.