There are only three available where I live, so I thought I'd start with my thoughts after having worn all three of them.

Let me start by stating that I wore the sensors as-is, without calibrating with finger-prick readings if calibration is available. I am not diabetic and do not rely on the sensors for accurate readings, so my opinions on these sensors should not inform your decision on which sensor to wear if you do.

Freestyle Libre 1, Abbott Laboratories

The first CGM I tried. Only supports NFC scanning, 6 hour history retention on-sensor. The sensor itself is pretty large and I experienced some aches wearing it. It may be because I didn't apply it properly since I wasn't expecting the loud sound the applicator made. The sensor lasts for 14 days and cost me 8000 yen, in a batch order of 2.

No real-time data and the 6 hour-only history meant gaps in my readings overnight, but I still think that it is alright. Still better than no CGM at all if this is the only sensor available.

Freestyle Libre 2, Abbott Laboratories

I'm wearing this one right now. The sensor is smaller than the Libre 1 and it now supports per-minute live readings via BT. The history retention is longer and I no longer see gaps in overnight readings, but since it updates live that's also less of a concern. The sensor's readings also aren't very noisy compared to the G7. The sensor lasts for 14 days and cost me 7500 yen, in a batch order of 4.

I like this one the best so far, and I haven't noticed any discomfort wearing it yet.

G7, Dexcom

The sensor is an oblong shape and is smaller than the Libre 1 and about the same size as the Libre 2, but longer. The adhesive is much wider and so it feels larger when worn. This was the most uncomfortable one of the three for me. I experienced a lot of aching while wearing this sensor.

The G7 supports live readings every 5 minutes over BT, with a (I think?) 24 hour history on the sensor itself. The readings are quite noisy, and fluctuate up and down a lot. Also, they appear to read generally higher than the Libre1/2, such that my baseline is about ~10% (90) more than on the Libre.

I like the G7 better than the Libre 1, but less than the Libre 2. It is the cheapest of the three, at 6500 yen in a batch of three, but it also only lasts for 10 days.

Phone Apps

LibreLink

The official LibreLink app for the Libre sensors is usable. There is no dark mode, and the amount of detail on the charts aren't user definable. This is probably fine if only used to check immediate readings, but as someone interested in statistics and historical readings I'd use an open source alternative if possible.

Dexcom G7 App

This thing doesn't run on my phone, so I can't review it. I had to use XDrip+ with my G7 sensor.

XDrip+

Open-source app that worked seamlessly with the Dexcom sensor. It's got highly customisable display and alert settings, plus all history data and settings can be exported so it can easily be backed up. It also has a nice widget and a detailed high priority notification display on Android.

It only works on my Libre 2 with Juggluco as a Eversense source. My guess is the OOP2 companion app required does not work with the Japanese Libre 2, since it displays NFC Invalid Data errors. Thankfully, Juggluco can take its place.

This is my preferred app for CGM readings.

Juggluco

By itself I've found this app clunky and hard to use, but it is able to set-up and pair with the Libre 2 sensor easily. In the settings, there is an option to enable Eversense broadcasting so it can send data to XDrip+, turning it into a replacement for OOP2.