Both of these medical blood pressure monitors must meet the same stringent specifications for accuracy. Pressure:+/- 3 mm Hg (millimeters of mercury), Pulse: +/- 5% of display reading. These values meet or exceed the provisions of EC directive 93/42/EEC(Medical Device Directive), and the European Standard EN1060, Non-invasive sphygmanometers Part 3:Supplementary requirements for electromechanical blood pressure measuring systems. The choice of device is basically one of convenience. Some people find the compactness of a wrist blood pressure monitor a benefit especially if one is travelling.Others prefer the larger buttons and display on the upper arm blood pressure monitors (easier to use and read).