Don't get a bagless. At least, as someone with allergies - I (my nose) can tell you that bagged vaccum cleaners are much better. The main HEPA filter lasts for ages (I've only changed my once in the last decade), thanks to the double filtering - the bag ls themselves are a filter, plus there's a second filter that sits in between the bags and the inside of the vaccum (which btw, you get free every time you purchase a ser of bags).

The main advantage of bagged is of course the maintenance/cleaning/disposal - when it's time to empty out your vacuum, just open the hatch and chuck out the bag and you're done - no risk of dust or tiny insects like dust mites etc spreading around. Especially in this era of microplastics - you don't want to inhale all the microplastics you've just vacuumed up now do you?