another Etrex20 user. V happy with it but you need to figure out your priorities. The Etrex are more multi-activity friendly, bulkier as designed to be handheld and use easily replaceable AA batteries. As theyre not bike specific they tend to lose some of the training-specific functionality, and use a completely different software to support them -Basecamp not Garmin Connect (at least for the 20), which might be a factor.
Munqe-chick has an 800, and talking to Connect is important for her as she has a Garmin GPS running watch (AND a Garmin Swim watch!) so she can log and review all her training and activities in one place. It also works with ANT+ cadence, and uses the same sensor unit to work with a wheel magnet so she can record her turbo trainer sessions. Does the 30 ‘only’ talk to HRM?
The only negatives to me are the brick-like bulk when mounted on the road bike and using only Basecamp instead of Connect.