When comparing SDDM vs Entrance, the Slant community recommends SDDM for most people. In the question“What is the best Linux Display Manager?” SDDM is ranked 4th while Entrance is ranked 11th.
Ranked in these QuestionsQuestion Ranking
Pro Supports both X11 and Wayland
Pro SDDM can start each DE
Unlike GDM which is stubborn in many ways, SDDM can start both Wayland and X11 sessions and any matter of valid session type, even if it's something obscure like Windowmaker.
Pro SDDM can provide full eyecandy
SDDM themes can include animated videos/gifs, background music/sounds, and any combination of the various QML animations.
Pro Recommended for Plasma 5 and LXQT
QML-based display manager. Successor to KDE4's KDM.
It doesn't support XDMCP.
Pro A Sandbox
Entrance is probably the most configurable and themeable display manager available.
Pro Does not need Systemd
So it can be used on other unix-like operating systems besides linux without the need for linux bindings.
Con It does not support some essential funtionality, like XDMCP
Con No Bluetooth support on the Loginscreen
Its not Lightweight as much.
Con Customizing is hard
Customizing this login manager is hard since you need to know QML very well.
Con A bit bloated
It requires Qt which is a huge dependency compared to other login managers.