I've used both systems. Each have annoyances. The Dexcom system can't be silenced and has an insane unstoppable firm "your sensor will expire in 6 hours", so unless you reset your sensor in the afternoon or evening this will wake you up and has woken me up at 4AM. I had to hide the Dexcom sensor in a watertight cigarette case to silennce the alarms. Both brands mobile apps hold you hostage and will not allow going do not disturb. I'm currently on Freestyle 2 with their own reader, which is silencible and I use a third party app Juggluco from some Dutch Diabetic. That app is quiet and gets realtime readings via bluetooth, it flakes out some times but it is great to have a second reader. Juggluco also gives me a bonus extra 12 hours at the end of the sensor life, so I'm slowly building up a reserve in days and eventually will have an extra sensor in que. https://www.juggluco.nl/Juggluco/index.html

Yes, the Dexcom alarm is obnoxious! I thought mine was defective the first time it happened!