I made the switch from DexCom to MiniMed two months ago at the same time as trying out a pump, and have found the MiniMed to be materially less accurate.
Make no mistake, the DexCom would sometimes get way off in its readings too, but the MiniMed unit seems particularly susceptible to not catching lows - I have had numerous hypo episodes, including several VERY SEVERE hypo episodes (glucose at under 40), where the MiniMed CGMS showed me to flat at 100-130+, such that even the glucose trend over a period of hours was NOT being accurately read/depicted.
And the funny thing is, they say you’re not supposed to use it to treat, always test yourself before you do anything and then it can’t hurt, but I disagree vehemently with this idea. IMHO, if the system is giving you false information about your level and/or the direction of your blood sugar, it’s better to be aware that you don’t know your level than to be told info of questionable value, because you will always attribute some level truth to it, and that can be dangerous.
I’ve also had a lot of problems with the system reporting bad sensors, etc., and have already had the transmitter replaced once and half a box of sensors replaced in an effort to find the problem. If we don’t have it figured out in a couple of months, I’ll be trying the Freestyle Navigator system.