Yup, this is the state of DC emulation as it is right now.
If you want the most coverage and technically "the best" then as @DOS76 said, Demul is the one to use.
Redream is great and is very simple to setup (no bios required) but does cost 5$ to get the resolution scaling and still doesn't support WinCE games or anything outside of Dreamcast. (As far as I am aware of at the time of this post)
The Flycast core in Retroarch is somewhere in between, it's free, relative easy to setup (you still need bios) and does have resolution scaling and WinCE support. It does support Naomi but none of the other stuff that Demul supports.