I only know one guy that still uses a UFO light and that's just cause he has a really tight space in his bathroom he is growing in lol.
I still use a blurple UFO. But of course it was my first LED maybe 15 years ago, and I only use it once in a while for rooting clones when I don't have a veg tent going. There is basically no good reason to buy one today, of course.
Unless one is on a ridiculously tight budget, QB or strip-based lights with some LM301 variant diode really seem like the way to go these days. You hit the nail on the head - it's about output, and nothing else reasonably priced is nearly as efficient. I speak from experience when I saw there are some generic and direct-from-China options that offer a LOT of light for the cost.
I've DIY'd a bunch of lights, for myself and others, mainly with COBs. I don't bother with that anymore, because there are so many nicely built, highly efficient panel and bar lights out there for reasonable prices. The DIY route can still be cheaper, but by so little that even my thrifty ass doesn't balk at the overall cost difference, because my time is worth something. At the end of the day, anything will work, to some degree. When I had almost no budget, 32W $1.29 CFLs from the Habitat For Humanity Re-Store got the job done, but if you can go from a $50 budget up to just $100-$200, you can get something that you will give you decent results in a 3x3 space, do so without excess heat and low power usage, and last a long time.