Why no Garmin?
I have a 201 -- I know old technology.
For my ride last Sunday on a beautiful if slightly cloudy day I finally gave up after 5 minutes of not finding a satellite. At IMFL the interior safety seal was not broken on a gatorade bottle and when I broke it I dumped quite a bit on my garmin and bike computer. The bike computer was fine, but the garmin was flakey for the rest of the ride.
Why no Polar?
I have a S625x and the bike speed and cadence sensor. I have had tons of problems regarding picking up a signal(I have read the signal boost post), interference from power lines, and the sensors just not fitting right on aero tubes or misaligning at inopportune times or potholes. Also without auto-pause the Polar does not give me accurate 10-mile split times.
OTOH my Astrale 8 has been rock solid in the same situations, but it does not do lap times. If the Astrale 8 had lap times it would be perfect as it does rear wheel speed and cadence.
With both the Garmin and the Polar I can't just jump on the bike and go. With a bike computer I just jump on the bike and go.
A wired bike computer is simplicity incarnate -- no waiting, charging, interference, satellite blockage, chest strap not damp enough, goofy mounting brackets, etc.
Swim - Bike - Run the rest is just clothing changes.