I'd make the choice based on two things:
1) Do you experience frequent power outages (blackouts or brownouts) in your area?
2) How critical is it that your computer not go down during those episodes, or that it have time to shut down cleanly?
When I went from a MacBook Pro to an iMac I hated the idea of having everything power off if the power went out for even a few seconds, and was planning to get a UPS. Yet I think we've only had one blackout that lasted for hours in the past few years I've been living in my current spot, due to a construction accident. Unplanned shutdowns are a nuisance and occasionally require some external drive directory repairs but otherwise I can live with them. A UPS would be a huge waste for me, so I just use surge protectors now.
In the past I've lived in places where there were blackouts and brownouts a handful of times each year, however. Were I still living in one of those places, a UPS would definitely be worthwhile.