When comparing LXDM vs LightDM, the Slant community recommends LightDM for most people. In the question“What is the best Linux Display Manager?” LightDM is ranked 2nd while LXDM is ranked 9th. The most important reason people chose LightDM is:
Some greeters such as the Unity Greeter look absolutely beautiful on LightDM.
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Pros
Pro Fast and fluent
Pro Works with Nvidia
Works well with Nvidia.
Pro Only two dependencies
Only needs GTK and Xorg-Server.
Pro GTK2 and GTK3 versions
Pro Works well on USB
A full install of arch on live USB works well on many computers with no text issues with LXDM.
Pro Beautiful interface
Some greeters such as the Unity Greeter look absolutely beautiful on LightDM.
Pro Best balance
Best interoperability, best balance between functionality and bloat, simplicity and candy, not distribution or GUI-tied.
Pro Cross-desktop
LightDM is not tied to any distro or desktop enviornment. You can use it on literally any Linux GUI.
Pro Good for DEs without a display manager
If your Linux desktop does not offer a display manager, you should use LightDM.
Pro Theme variety
There are a wide variety of themes available for LightDM, from console-like UIs to ones that utilize webkit2 to create flashy and dynamic login interfaces.
Cons
Con Requires Xorg-server
Currently LXDM does not support wayland.
Con Depends on GTK and its dependencies
Con Not really lightweight
How lightweight it is depends on the used greeter, but they all require much more dependencies than other lightweight greeters like XDM or SLiM.
Con nVidia driver and kernel woes
It's been on the decline lately where it's only stable under a very specific mix of kernel and nVidia drivers.
Con High RAM usage
It uses more RAM than other light (xdm,slim) display managers which results in more overhead.
Con Poor/missing documentation
Con Hard to configure
Lighted.conf doesn't even work.
Con Autologin never worked
After 4 years of using LightDM, I never managed to make it autologin my user in the system and there are always problems with the graphics driver. Crashes too often and requires manual restarting which is dull. Not to mention the developers update it once in a leap-year.
Con Feature creep
Most people don't need (or even know) all features of LightDM.
