Hard to answer this question because there's a tradeoff between noise, airflow, and surface area with air purifiers. Eg if you cover your ceiling with air filters, the noise will be minimal.

I'd say if you have enough output power and are only limited by uv exposure, it's vastly more effective. I had to buy a couple of expensive Clean Air Kits purifiers to get ~25 air changes per hour in a smallish room, but 100+ equivalent ACH is possible with far-UVC, either by using light filtered to 222nm or keeping it in some kind of ceiling louver that traps the light. Not sure how the cost compares though, as they seem to be limited by output power / $ rather than safety limits.

I'd recommend playing around with Illuminate. Depending on the room size and shape, far-UVC can range from mildly less effective as a good air purifier on high to far more effective.

For example, lets say you have an Aerolamp in the corner of a tiny room (10ft x 7ft x 8ft). You'd need to dim the lamp to 70% to protect people who are near the corner. Illuminate calculates (guv) a CADR-equivalent for a range of pathogens, and taking the median I get 216 CFM. Then let's say you instead put it in a cavernous room (50ft x 50ft x 50ft). Now you can easily run it on full power (guv) and I get a median CADR-UV of 1,979 CFM. Even if you run it at 70% power to keep it apples-to-apples the median CADR-UV is still 1,354 CFM. (sheet) Of course most rooms will be well between these two extremes!

Compare to the AirFanta 3Pro at 413 CFM on high (though it's noisy enough on high that I only run mine that high if I need to clear smoke).