It's like saying "What's the best car to buy ?" , I'd say a Maclaren that's if you can afford one.
It's all down to budget,
The comparrsion should be compared to price so best under £50, best £50-£100, best £100+
I've had cheap £25 android that do as they say on the tin and a 96max (slightly deaer) 2.4g-5g wifi.
But for me its a Fire 4K all the way. They regular come on offer at £30 and for me it at roughly £30 it beats everything hands down.
Buy and ethernet adapter and hard wire it and your away.
Like I said, what are you prepared to spend and what you will get for the money.
At the end of the day it's only tele. I've had a 4k and it does the job fine