When specification tables look the same, the real differences often come from warranty, usability, consumables and everyday limitations.
Define your use case first
The same product can be excellent for a small apartment and frustrating for a large family. Compare for your situation, not an abstract “best.”
Read manuals and limitations
Manuals often contain details missing from marketing pages: operating limits, maintenance and actual feature behavior.
Compare warranty and service
Two products with identical specs can differ greatly if one has accessible service and spare parts and the other does not.
Check ownership cost
Filters, accessories, cartridges, apps and subscriptions can make the cheaper model more expensive over time.
Bottom line
Keep the solution simple: start with the most likely cause, change one factor at a time, and observe the result. That makes it much easier to identify what actually works in your situation.