I use both of them in parallel testing amd have done for well over a year now, I too get misreads from my SD Codefree and need to retest. I have noted that the Codefree ALWAYS reads higher thn the Dual (or the Abbotts I used to use) and the average difference between them comes out at 1.3 mmol/l over several months. But I can get differences of up to 2,6 higher before I declare a misread. I also now retest if the difference is less than 0,5 Sometimes I do a second retest just to go with the majority opinion. I think the Codefree is sensitive to something else in the blood (oxygen level, or lipids, or haematocrit value which fluctuates too. The Dual is IMO more reliable.
Yes the Codefree strips are cheaper, but not by much when VAT is taken off. There is no bulk buy option on the Dual, and no discount codes that I know of. However, the Dual does have the ketone capability that the Codefree lacks,
My SD Codefree is getting forgetful, and cannot keep time at all. Set the time and within a short while it is rubbish, Days seem viable,just not sure if it is day or night when writing up the logs. Others report this happening to them.
The dual has upload capability that I do not use myself, and their support software is not quite what I need, Think it uses a special cable that I was given, but that was when it was launched, so probably needs to be purchased.
I prefer the Dual myself, and my GP likes it too since I get strips. I self fund the SD since this is my backstop check for misreads.
My SD has always read higher than my Accuchek, my 2 XCEEDs, and my 2 NEO meters, and now the Caresense too. It is either wrongly calibrated to plasma, or is is being affected by an impurity in the blood.