I think ultimately you should read over the different forums and get a feel on what issues are coming up, and decide on what you can live with.
The Roomba's are overall pretty good. The main and biggest flaw is the CHM letting hair/debris enter the gearbox and causing issues. It has been overcome with a CHM sealed-bearing mod, which a member offers this service. I think you might want to get the model that has the Lighthouses, so you can break up your home in 'zones'. This is an invisible barrier.
The Neato is pretty good, but it has issues as well. the most frequent issues are the RPS error, and the wheel spring breaking the plastic connector, thus needing replaced. You have to use magnetic strips to barricade an area off-limits, which some might not like.
I have very little experience with the LG, and Samsung.
The Karcher is a well-built robotic vacuum, but it comes with the heaviest price tag, which turns some people away. There are the limitations as well.
Every robotic vacuum has their issues. Every robotic vacuum can get stuck. Some robotic vacuums require maintenance more frequently than others. It all depends on what you really want, and can live
Head on over to the Review section
to read up on the different makes/models of robotic vacuums. Unfortunately, there is no cut and dry answer to give you (Too many variables). The robotic vacuum I personally use, might not work in your environment, or other variables that doesn't mesh (Too expensive, worried about warranty, wrong color, feature you want is missing, etc)..