None are perfect, most are adequate. Difficult to tell how accurate they are since what do you test them with ? In any case it's usually the direction your weight is going over time that's more important than whether it's reading slightly high or low.
Of course you really need to have a hard floor to use them on.
I'd buy the cheapest that you like the look of.....because they all contain load cells (the part that actually does the weighing) that are, by their design, accurate and difficult to get wrong. Similar to the quartz oscillator in watches...pretty much the same accuracy whether you spend a fiver or a few hundred pounds.
The only way you can be sure of accuracy is to take your scales to the local Surgery, persuade the nurse to weigh you on their scales, then get onto your own scales and compare the results.