Gantry 5 has arrived for Grav.
Would you prefer Grav by itself or Grav+Gantry.
Please suggest "why" in general terms.
I'd add one important thing.
Grav was built by members of the RocketTheme team using many of the same technologies that Gantry 5 is built on. They fit together like a glove because they were literally made for each other. Same basic UI, same YAML & Twig codebases, etc.
Gantry 5 wouldn't be what it is today without Grav. Grav wouldn't have been possible if we weren't working on Gantry 5 and the technologies it incorporates. Each benefitted greatly from the work being put into the other.
If something about Grav creates an obstacle for Gantry 5, it's quick to be resolved because the same team works on both of them.
That's a really good reason to give it a shot.