The biggest difference between the two meters is that the accu-chek is reporting a whole blood glucose figure, whilst the optium xceed reports a plasma blood glucose figure (the meter multiples the value returned by the test stick by 1.12). So the Xceed will report a higher figure, by around 12%, additionally, there is also an "acceptable" tolerance of around 10% between readings.
So, multiply the accu-chek by 1.12 which will then give you a plasma blood glucose value of 5.8 mmol/L. Which, is still more than 10% different than the reading provided by the Xceed.
Thankfully, blood flows continuously around the body, so unless you can test the exact same drop of blood more than once under the exact same conditions you are unlikely to get the exact same reading between meters.
Personal preference? I have to say I prefer the Xceed (I have a Bayer and an Accu-chek as back-up meters), primarily because it does give an approximate plasma blood glucose reading rather than a whole blood reading - because it saves me having to multiply by 1.12.
Regards, Tubs.