I have the new Garmin Virb Ultra 30 on the front and the Cycliq Fly 6 on the rear

I spent a long time deciding which front camera to buy (The Garmin Virb or the new GoPro Hero 5), but the Garmin seemed the better option for cycling, as it connects to all my garmin sensors (heart rate strap, speed sensor, cadence sensor etc).... easy to use and also has voice recognition (which works).... battery lasts just under 2hrs, but you can charge it on the go. It does not come with a micro card, so budget for that aswell. (I spent close to £100 for a 128 card

The Cycliq Fly 6 is a brilliant rear camera (battery lasts approx 6hrs) and it's a pretty decent light aswell. Mine is the newer version with the velcro strap.