Which is the best value for money? I am looking for something affordable. I can pay a reasonable amount monthly for consumables for it.
Do your part as a consumer and shop around a bit to drive prices down... good luck!
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.
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.
(I've never tried the dexcom and am very happy with my libre)