I would definitetly recommend the Dexcom G7. As I come from the libre3 I have to say that the G7 overall feels more sophisticated, yet alone the overpatch they send with each sensor will help keeping the sensor on my arm. In the past the libre3 often just fell of during my swim training.
Further, libre3 is often just not supported by third party apps or pumps or other. They do not provide an official API, that might be helpful for tracking your clucose. Back in the days I used and contributed to https://github.com/timoschlueter/nightscout-librelink-up to periodically fetched my sensor data from librelink and stored it my nightscout, that runs on my server at my home. That helped a lot, but it was more than a hack.
As someone using a freestyle Libre 2, I’m also curious.
From what I know, I think the main reason is that the Libre needs NFC vs the Dexcom’s Bluetooth… except that Abbott recently updated (!!) the software and now Bluetooth works at par as the dexcom.
Some people have better sensitivity with one or the other I agree, but both are fairly solid. The Libre is smaller though, so I prefer that.
I have read a few people who say they prefer the dexcom because the freestyle is pre-calibrated and Abbott's software doesn't allow you to calibrate the device.
(I've never tried the dexcom and am very happy with my libre)
