In my experience, the bagless vacuums are at their best when sucking up relatively large items like hair, peas, etc… because they tend to settle out well in the cyclonic separator portion. Fine dust and stuff like flour aren’t so good, because they’re not heavy enough to really settle out much in the cyclonic part and the filters end up filtering them out, reducing their life.
My vacuum has the best of both worlds- it’s bagless, but 2 of the 3 filters are washable and don’t need replacing. Only the final HEPA filter needs replacing, and it’s both pretty cheap and lasts a LONG time.
I think the canisters of Dysons work really well at capturing a lot of the fine dust. I recently rigged up the canister of my Dyson as a pre-collector to my shop vac when I had to sand over 1000 sq feet of skim coated walls in my house. There was virtually no drywall dust in the shop vac. I had a drywall filter on the shop vac and added the Dyson so that the shop vac’s filter wouldn’t get clogged. At the end of the job, the shop vac’s filter looked practically new. There was just a bit of dust on it. The Dyson canister alone was able to capture practically all the dust.
I’m not sure that all bagless vacuums can do that. A lot will depend on the design of their canister. But the Dyson is so effective that even if the exhaust path is leaky, there’s hardly any dust going out there anyway.