None of those tools (and I use the term loosely) are scanners. They are OBDII code readers. That means they won't work on OBDI cars and they won't work on anything but generic engine codes. If they give any data it will be OBDII generic which is considerbly different than MB in many cases.

It hard to say they are better than nothing as a little info can be a dangerous thing. They specialize in a little information.... very little. I could diagnose almost nothing with one. But of course if you don't know anything a little can be relatively large. No more help but a great guide to throwing parts. I would suggest bolstering your arsenal with these: http://www.creativedice.com/productinfo.html

What you get with these tools is of so little value that Autozone gives it away free.

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician