I have both; I don't do edge banding either.
The M18 is more flexible if you have all the attachments/bases.
Also obviously cheaper to have "extra" routers laying around set up for certain things, or certain bases.
You can run larger bits than you can fit in the MFK, in some of the M18 bases.
You also have more depth adjustability (fits longer bits too) on the M18, even without the plunge base.
You can also get a base for the M18 similar to the MFK 700 base, which makes it almost as secure when routing.
https://www.woodpeck.com/stabilmax-trim-router-base.html
The MFK is better at specific things.
Better dust collection.
Slightly better oblong base.
Slightly better ergonomics.
There is the 1.5* base available for the MFK (I don't have this), which is something you can't do with the M18. Just a slightly different angle on things.
You also don't have to worry about the battery running out on you in the middle of a large cut.
The MFK is slightly limited as an all around trim router. But what it can do it does very well.
If I HAD to pick one or the other I'd probably go with the M18 for the extra versatility.
I find the MFK more enjoyable to work with and I grab it over the M18 if possible.