Twice the data rate or four times the range. That's a really important distinction.Bluetooth 5 carries twice the data at four times the range. If this device is connected to your smart phone, that matters. Especially if you don’t pay for cellular in the watch. Also if you’re ever away from your phone, which I constantly am when I walk around my house.
https://www.androidauthority.com/bluetooth-5-speed-range-762369/
You'll likely get one eighth the data at four times the range, and 1.7 times the data and a quarter the range.
That's not nothing though. Most of the time with the watch on your wrist and the phone in your pocket you'll benefit from the data rate and an eighth the data over longer range in your house is better than none...
Still I haven't noticed that the data rate to the watch is my limiting factor for anything but software updates, and WiFi seems like the preferred long range communication when at home, rather than point to point over BT. I think I'd benefit more from better WiFi than bumping to BT5...