Kept the Polar Loop for about two weeks...overall, I liked it but it would never update the unit when connected to Polar Flowsync software. Everytime I connected it, it would prompt me to upgrade, I would say yes, it would do the download, 'do' the upgrade and restart. After the restart, it would prompt me to do the same upgrade. Tried it on Windows 8.1 and 7 machines and the same thing happened. After doing a chat with Polar CS, they wanted me to send it to them so they could look at it. I decided to return it.
After returning it to Amazon, I went to REI and got the Garmin VivoFit. The Loop had a cooler 'wow' factor to me (since it looked like a modern bracelet with red LED's while the Garmin looks like a plastic toy, but totally comfortable to wear 24/7.
The Garmin seems to have lower counts for steps, calorie burn and heart rate BPM's. When using the chest strap, the Polar would drop a signal (every 10 minutes when I first got it but down to just two or three times a workout when I returned it so I don't know if it had to get used to you)...
The biggest advantage for the Garmin is the battery. It has two little watch batteries inside that can replaced by the user. According to the manual, they should last a year. I charged the Polar every 3 or 4 days. You to remove the unit to charge it because the charging port (which connected to the cable magnetically) was under the display. The Garmin display has no backlight so it can't be seen in the dark (which is probably why the battery lasts a year).
I personally liked the Garmin software (both the PC and mobile app) over Polar but that is just personal preference. Garmin's mobile app is available for both iphone and android while the Polar only has an app for iphone (that just seems ridiculous)....
I would definitely have to recommend the Garmin over the Polar Loop based on the time I have had with both of them.