A companion app ties you to one brand of cuff
This is the part nobody mentions when you buy the monitor. Omron Connect works with Omron monitors. Withings Health Mate works with Withings. Beurer HealthCoach works with Beurer. They are not competing apps you choose between. Each one is the software half of a specific piece of hardware.
That matters in three ordinary situations. Your monitor breaks and you replace it with a different brand. A second person in the house gets their own monitor. Or you have three years of history in one app and the company changes the terms. In each case the readings and the app are joined at the hip, and moving is a manual export at best.
Typing the numbers in yourself avoids all of it. It costs about eight seconds a reading. In exchange the log is yours, it works with whatever monitor you own now, and it keeps working with whatever you own next. That is the real trade: a little friction for no lock-in.
We are not going to compare those three apps feature by feature here. Our sister property does it properly, brand by brand, and duplicating it would make both pages worse.