Originally Posted by Phinias
Which one is recommended and why
Many people have used the ScanGauge II with success, especially to help you know when to downshift, in order to reduce load on the engine (aka Lugging) by monitoring LOD, boost, and gallons consumed per hour while driving...as well as reading many (but not all) and clearing some (but not all) of the codes that might appear. That said, the SGII is older technology, with a smaller and simple LCD display, and some people like the more modern UltraGauge.
With the Sprinter, no standard/generic obdii code reader will be 100% accurate, as it makes use of the interface in a somewhat proprietary way. the code you might see could sometimes be misleading or be related to other codes you do not see at all.