I do a "both big and small ship" universe--as mentioned above, big ships are for the wargamers, small ships are for the roleplayers, and at least my campaign has a heavy emphasis on roleplaying, which means small ship actions (even at the mercenary level; the next adventure I'm planning is going to be a battle between a company-sized force and the PCs' force of two fireteams and local levies--yes, it's definitely going to be a "Seven Samurai" type encounter, but with the PCs on the offensive. Nobody said mercin' was easy.)
The character scale being the small-ship scale means that typical interaction with local authorities are generally with patrol corvettes. And yes, I really like the MgT2 convention change from "patrol cruiser" to "patrol corvette," especially because my players, new to Traveller and not having seen images of the Patrol Cruiser, just assume it looks like a giant Chevy Corvette with rockets on the back and a bunch of guns, but the message they get is the same--a fast, pointy, dangerous thing that's tougher than they are, but not overpoweringly so. To facilitate a Traveller universe with large starships but also a relatively chaotic, space-frontier atmosphere, I assume that Imperial Navy forces are numerically small and localized, but structurally big and well-supported; while the Tigress BatRon is away, which is most of the time, the small-ship mice will play, although even the 400 ton house cat (in the form of the aforementioned patrol cruiser/corvette) is more than a match for a mouse--the key thing for the mouse is to be where the cat ain't, and in space, there's a whole lot of ain't to get lost in.
Big ships are good for back story--PCs who served as ship's troops on a Ghalalk or a Plankwell class and have a contact or ally in the ship's captain, or a large interstellar liner as settings for adventures where you need more room to hide things than a 600 ton passenger liner. Or for generating a "wrong place, wrong time" for the PCs to struggle to not be near when it arrives (a good push towards or away from places the GM doesn't want the players to go.) Big ships can practically be worlds on their own. Small ships, on the other hand, are characters--characters may have visited a heavy cruiser, but they know that free trader.