We got one last year which mops as well. I don't think the hoover function is any worse than one without a mop, it seems the same. I am not convinced the mop function is really worth it, though, because it's basically impossible for it to do anything other than gently swipe a cold, dirty cloth over the floor, which to me feels like it's just spreading germs around more than cleaning. I suppose perhaps if you really perfectly mopped the floor to within an inch of its life before running it for the first time and then ran it religiously every day and get several spare mop pads and keep swapping them??
But basically the cloths are tiny, if you were using one yourself you'd use a much bigger one (or if you think of the surface area of a mop for example) and keep folding it over or at the very least, rinse it out. the one we have, all the water stuff is held at the base, which I think is standard because I don't think it would be practical for the vacuum itself to hold water. You can add cleaning solution to the clean water side, which we did originally but their own cleaning solution is so overpriced and is basically just standard floor cleaner anyway, so we switched to sticking some Dettol stuff in it, which works just the same. It does get clogged up with limescale easily (which DH attributes to the non-branded cleaning stuff and sometimes runs it without soap) and I CBA to fill it with distilled water. I don't know if it heats the water it uses to clean the pads but it would be completely pointless, because as soon as it's travelled 30 seconds away from the base, the pads will be cold again. If you think of how often you rinse out a mop or even just a cleaning rag, it's impractical when it can only do this at the base, so it just keeps using the same dirty pad for 20 mins or more before going back to the base to clean it. They usually only come with one set of mop pads, so I can only assume you're meant to leave them on through multiple washes. We did get a set of replacements and I try to remember to swap them out but if it's up to DH he only swaps them once every few weeks 🤢
It just seems a lot more needy than the ones we've had which were just vacuums. Those would get stuck occasionally and the sensors would get dirty so it couldn't dock properly but that was it. The addition of water seems to make it much more disgusting and introduce a whole load of other issues. Is our floor marginally cleaner than us never really bothering to mop it?? Maybe? I don't feel like our floor is noticeably dirty or anything, but I just know if I was mopping myself, I would not take a miniscule cloth, a cleaning spray and keep using that for 20 minutes, then rinse it in cold water, repeat, and then leave the same cloth to use tomorrow. Because that is disgusting and not clean.
Plus, when you empty the dirty water it stinks like something unholy, and there is always something gloopy growing in it - I tend to flush the contents down the toilet and chase it with loo cleaner otherwise it completely stinks out the entire house for ages, then scrub out the dirty container, but again, DH will just stick the empty (not clean) container back into the machine. I don't think it cross contaminates, but still.