It's all about what they need the ship for really. Is this design meant to service the Federation's safer interior (frigate) or push the borders of known space further out into the perilous unknown (cruiser)?
Since the whole point is that we're replacing the aging Curiosity, what was the Curiosity for?
The Curiosity-class cruiser was United Earth's first dedicated survey ship, designed to investigate safe areas of space for potential colony sites and points of scientific interest.
Seems straightforward to me.
[X] Highly specialised, short ranged, minimally armed. (Frigate: ~200k)
Also, if we build a frigate now, I think that makes it more likely we get to do a big explorer next.