What is best for Verizon Fios - X4S (C7800) or X6 (r8000)

> I am moving to Verizon Fios 1G and was getting confusion of what is
> better the X4S (C7800) or X6 (R8000)? [...]

   A Netgear model Cxxxx is a cable-TV-type modem+router.  To be sure,
you should ask Verizon (or do more research), but I'd expect that to be
largely useless with Verizon Fios.

   A Netgear model Rxxxx is a router.

> [...] Could not find anything that compared both [...]

   Because a modem+router and a router are not functionally equivalent.

   Knowing nothing, I'd expect Verizon to provide some kind of (simple)
gizmo, like, say, an optical network terminal (ONT) which would let you
connect and use the router of your choice.  Which could be a mesh
system, if that's what you want.

   They might prefer that you got some all-in-one box from them, but I
doubt that it's a requirement.