Modern Chess Openings vs Fundamental Chess Openings?

Which covers more variations? Which goes more moves deep? Which has more explanations?

I'm especially interested in smaller lines like 1. e4 d5, and 1. e4 g6. Which goes into more detail on those?

FCO is a more of learners guide as it explains ideas of the openings etc

MCO is just most lots of theory with little or no comments which isn't that useful for lower level players.

MCO and books like it are reference books .... they have very little text and practically no instruction. They arent meant for beginners but stronger, more experienced players. When I was beginning Ruben Fine's : Ideas Behind the Chess Openings helped me a lot. MCO was just a lot of gibberish  I couldnt make use of... yet.