I am using at the moment the Codefree as the strips are cheap though I think that probably the cheaper the strip the less accuracy as the accuracy probably depends more on the strip than most other factors. Some of the factors that effect accuracy are:
the quality of your meter
the quality of your test strips
how well you perform the test. For example, you should wash and dry your hands before testing and closely follow the instructions for operating your meter.
your hematocrit (the amount of red blood cells in the blood). If you are severely dehydrated or anemic, your test results may be less accurate.
interfering substances (Some substances, such as Vitamin C, Tylenol, and uric acid, may interfere with your glucose testing). Check the instructions for your meter and test strips to find out what substances may affect the testing accuracy.
altitude, temperature, and humidity (High altitude, low and high temperatures, and humidity can cause unpredictable effects on glucose results). Check the meter manual and test strip package insert for more information.
store and handle the meter and strips according to manufacturer’s instructions. It is important to store test strip vials closed.
Smart meters are more about how the data is handled and presented not the accuracy of the data.