I had this device in use for about 1 year and was able to reach a maximum of 45 Mbit/s via the SIM card, but only 15 to 20 Mbit/s. I would therefore not recommend the device. The biggest difference between the MR400 and MR600, the MR400 can only do 100Mbit LAN and only 150 Mbit/s LTE download speed. The MR600 can do Gbit Ethernet and a maximum of 300 Mbit/s download speed. The MR200 is actually nothing, it has totally outdated WLAN in it. The MR600 and MR400 have the same WLAN, but it's very poor. I couldn't even get from the living room to the bedroom, which is about 7m.

I wouldn't recommend either of these devices, in the meantime I'm using a device that can do both very well WLAN and also LTE download. Set up in the same place I now get a download rate of over 200Mbit and the router from Netgear can even download a maximum of 1.2 Gbit (it has Cat.16, an Archer MR600 has a maximum of Cat.6). Sure, it costs more, but in return you get incredibly good Wi-Fi and absolutely flawless download speeds via LTE:

Netgear Orbi 4G LTE WiFi

The device is more expensive, that's true, but in return you have hardware that can really do something. And the WLAN of the Orbi LTE could also be expanded.