first off i don't believe the hybrid/zero gravity case is being offered at the shop anymore especially with new Metro purchases.
looking at the site it lists this:
Case Included
- NYC models include your choice of our custom PortaBag or hardshell case.
- Metro basses ship with a gig bag.
so whoever stated that Metros include this - it actually changed if you get a newer Metro. however if you buy a metro through a dealer, i would ask and check first.
as far as differences between the the hybrid and PB. the PB has the straps and handle so it's easier for transport. the handle on the PB is better constructed and feels like it has more mass too it. The PB also seems to secure the bass better all around. There is also more padding especially towards the bottom of the bass when your standing it vertically.
The hybrid does a pretty good job, but "giving it a little shake" to test if its secure, there is a bit of movement. To me at least, i also feels there's more usable storage on the PB as well, compared to the hybrid.
@TedH if i were you i would keep the PB