@marios239 

I just bought an MR550 on Amazon, and it is actually a mr500 (mr500 appears on the configuration page)

  @marios239 
I wouldn't recommend buy any of the TP-link mobile routers. They're slower than competitors and you basically get no suport if there's a firmware bug.
People wait here for years for known bugs to be fixed, just read any of the threads.

  @marios239  I don't know about the other 2 but stay well clear of the MR500 (and if the 550 is the same as the 500, that one as well). I have had mine for about a year now and have had so many problems with internet regularly disconnecting. There have been several firmware updates but none have fixed the problem. There is a thread purely for this fault

  @marios239 

I've got an MR600 v2 and it is VERY stable and reliable. It is working at full speed (100mbit) which is as fast as it can go for a year now, without any issues.

I did upgrade the firmware once, just to see if I can get it to work faster but thats about it. Just in case its relevant, I'm only using it for internet connectivity, WiFi is disabled because I'm using the intfrastructure of my home with WiFi and ethernet cables.

  @DonW55 

I have problems with the mr550, which is the same as the mr500, but I still had more problems with the 6400