I rate mine.
Primarily wanted the course following function without having to go to a fully mapped unit. It is basic but I’ve not had any real issues on my road or CX bike. Not tested it on complex off road stuff like round the woods though.
Only negative thing is Garmin Connect and Express, absolute GARBAGE!!
all routes have to be manually created on garmin connect,
The above isn’t true though. You can load from any source as long as you convert it to FIT format with gpsies.com. You can then simply drag and drop the .fit file to the NEWFILES folder on the Garmin within Windows Explorer. It will then appear as a course on the device. The only problem I’ve noticed with this method (it’s done it once) was the dist-to-end function didn’t work whilst on the ride.
You do have to use Connect to upload to Strava if you want to use the Bluetooth method, alternatively you can upload direct on a computer.
Not used HRM or cadence sensors so can’t comment on those. If you’re not arsed about the Bluetooth connectivity the 20 would be just as good I guess.