I've got an LG Hom-Bot (Roboking), but so far haven't been able to use it.
I did a lot of research and the Hom-Bot is probably the best out there. Got it a couple of years ago. AFAIK, it hasn't been surpassed yet, but I haven't seen how the Dyson & other latest models compare. They are made primarily for the Korean market though, so used to be impossible to get in the UK. I got mine from
myrobotcenter.co.uk who have been importing them for a few years now and selling them online with a proper warranty.
Unlike the Roomba which moves around randomly, the LG maps the rooms as it goes and can do a whole floor. If it misses a spot it comes back to try later. When its battery gets low it goes back to its base station to charge, then picks up where it left off.
Trouble is, I got it just before moving and in my current flat I don't have the required 2 metres of unobstructed wall space for the base station :(
Roombas IMO are overpriced and are based on AI technology that was advanced at the time, but is now at least 10 years out of date. They have been milking the name (to most people Roomba and robot vac are synonymous). They haven't moved on or really innovated at all. The most expensive high-end models are only a small increment above the base models. Others like the LG are far more advanced.
Beyond that it's mostly a tradeoff between vacuum power and noise, although some of the cheaper ones are prone to issues like the early Roombas, like getting trapped on wires, curtains or under beds. I believe even the top end Roombas still have occasional issues with this because they only have the most basic hazard avoidance systems, which are essentially hacks on top of the basic "insect" random-path AI (IIRC this was the founder's PhD project) in response to all the early customer complaints about them getting stuck all the time.