LP+ uses control solutions to calibrate. Tested those control solutions on a LP2 strip, always higher than the range, which is not that large. On avg from what ive tested about .4-.5mmol higher.
Also, anecdotally, the Norwegian Triathletes use the LP+ and show their values in training. They state their lab tested threshold values in many interviews and test in their youtube videos and show the results. Pretty much 1:1. Of anybody, i would assume with the amount they are testing and how freakishly they measure every variable in training, they would probably be using the meter closest to the lab.
I think many like the LP2 because to me its certainly better to have the strips individually wrapped, especially for transporting them. Also, LP2 probably more available than LP+ in EU than in the US.