What are the pros and cons of applying for a Non-O visa based on marriage versus an extension of stay in Thailand?

Easier is in the eye of the visa holder. What is easy to you might not be easy to someone else.

People opt for the year-long, multi-entry Non-O visa based on marriage from a thai consulate for a variety of reasons. they travel extensively, they cannot or don't want to meet the financial requirements, etc.

As

@Robert ******

pointed out, the primary difference is that you must meet the financial requirements to get a yearly extension whereas depending on what thai consulate you go to for your Non-O visa you don't.

Another difference is a yearly extension is sold as NO-re-entry <- that's because you're already IN thailand when you get it. This means if you're going to leave the country during the year extension you would also need a re-entry permit (1000baht for a single or 3800baht for a multiple). A year-long, multi-entry Non-O already has a multiple re-entry permit "built in" to it so you can come and go all you want for the year and get stamped in for 90 days every entry.

Another factor is the paperwork; you can get a year-long, multi-entry Non-O visa from a thai consulate based on marriage with minimal documentation (and without your thai wife being there), where as with a yearly extension you're gonna need a pile o' paperwork, photos, AND your thai wife needs to be there when you apply.

The last thing I can think of is, yearly extensions go under consideration for 30 days before you go back and get it inked into your passport whereas year-long, multi-entry Non-O visas are issued on the spot (even though you pick it up the next day ;) )

That's about all I can think of anyway :P