What are the pros and cons of a DTV versus a marriage visa for expats planning to live in Thailand?

With a marriage visa, you only get 1 year at a time (90 days per entry if using a multiple entry marriage visa obtained abroad) but you are work authorized once you apply for a work permit.

With a DTV, you can't work for a Thai company.

However, unless you're expecting to receive a job offer for working in Thailand soon, you might as well apply for a DTV and then, should you get a job in Thailand, you can always convert it to a non-B plus work permit or go out of the country for one, in order to ensure you are able to work legally in Thailand.

Thus, a DTV is better, provided you don't have a need to work in Thailand for a Thai company.

A marriage visa is better, if you do have that need.

Marriage Visa you can work

DTV you cannot work in Thailand

If you're planning to work locally (ie getting paid by a Thai company) you can't use a DTV. Otherwise, the DTV would offer a 5-year stay at once so it's better.