I think they both have their part in the 3d printing world. Pretty much like how to cut wood, you have a jigaw (quick and inexpensive); and you have a table saw (precise but costly). Depends on what you want to achieve, both tools are useful.

That said, I prefer SLA. FDM quality isn't as high-res for my personal taste on what I want to do. As "sketches", it works great. As an "end consumer product", I wouldn't put my name on it to sell. Nothing will be cheaper to product than FDM, so an other types of printer material will be more; we all just have to accept that. That said, SLA prints are still inexpensive when compared to powder-based prints.

SLA printers aren't common only because the technology's patent only rare out recently. We're seeing the first family of home-based SLA just within the past year. There are some that are the same price as mid-range FDM printers. They are faster than PDF printers which in itself is a selling feature over FDM for some people. It required s small clean station area, which may deter some users.

There will be a split between users, I don't see FDM as going away but I see them as a low-mid entry choice, while SLA will be mid-upper entry choice for the hobbyist.