I just switched from my powertap yellow head unit to a Garmin 520. The powertap interface and features are way better than garmin. Things like auto ride start/stop at stoplights, and explicitly having to 'save' or 'discard' a ride. Also, the powertap is easy to cycle through display items (watts, avg watts, 20 min peak watts etc...), with the garmin I can't do this while riding.
Of course the garmin shows speed when I don't have my PT wheel on, which is the main reason to switch., but the interface of the Garmin 520 is so clunky I wouldn't buy another.
You can do all of those things with a Garmin.
Garmin has auto-pause based on a minimum speed.
I believe you have to confirm before discarding a stopped ride.
The 520 is touch screen with multiple 'pages' that can be swiped left or right to change.
I'm not a Garmin fan anymore, though. Just wanted to note you
can do those things.
I had a Garmin 500, then 510. Both gave me enough fits that when Garmin finally cycled me up to the new 520 I just sold it and moved to Stages Dash.