I have only used Medtronic's CGMs, both the Sof-Sensor (aka "the Harpoon") and its replacement, the Enlite. I am in the US so I only have experience with the first version of the Enlite, not the slightly "enhanced" version used outside the US.
Based on what I have read, most people prefer the Dexcom CGM for various reasons. Some focus on the accuracy, others on the ability to extend use of a sensor for up to two or, in some cases, three weeks. For others it is a cost issue.
While Medtronic CGM can and does work, it tends to be more finicky. My personal guess is that this is a consequence of the physical design of the Enlite. If one does not get the insertion & overtaping of the Enlite done right, then the sensor probe can be jostled which in turn leads to horrible inaccuracies. All of which are then blamed on the innate capabilities of the system, which I think is often a mistake. But ... whatever.
The bottom line is that based on what you said about Medtronic being "horribly expensive" you probably want to go with Dexcom if the cost is lower for you. If you were already using a Medtronic pump then perhaps that might be an incentive to also add on their CGM. That's how it worked for me. But if you don't currently have a compelling reason to go with Medtronic, then I'd say look at Dexcom and see how that might work for you.