Cat acceptance and body room
Open-top robots remove the need to pass through a doorway into a globe. That can help large, long-bodied or enclosure-averse cats. The cat can keep its head and upper body in open air while using the litter bed.
Enclosed robots create a more defined interior. Some cats are completely comfortable with that; others are not. Past behavior around covered manual boxes is more useful than a generic claim that one format is universally preferred.
Odor control is a system, not a shell
An enclosed litter bed can reduce direct room exposure, but the important odor path is what happens after waste is separated. Drawer sealing, carbon filtration, litter clump quality and emptying frequency matter.
Open-top designs can still seal waste below the litter bed after a cycle. That means the right comparison is the full path from fresh waste to stored waste, not whether the top is visibly open.
Cleaning and failure modes
Open designs can make the litter area easier to inspect visually. Enclosed globes may contain scatter more effectively but introduce more interior surfaces to wipe. In both cases, sensors and moving parts need to remain clean enough to function correctly.
Before buying, read the current manual and identify which parts are removable, which can be washed, and which must stay dry. Ease of deep cleaning matters more over years than it does on day one.
How to choose
If the cat is the risk, choose the geometry most similar to a box it already uses willingly. If the household is the risk, compare odor storage, footprint, drawer access and cleaning workflow. Then use ownership cost as the final tiebreaker instead of starting with price.