Steve himself said that ship size tends to increase with tech level- as in real life. A civil war frigate is tiny compared to a modern day frigate.
I very much keep my designations in line with role, rather than size. Destroyers are the gun line, Escorts provide support, and are frequently bigger than the ships they're supporting, especially if I put a jump engine on them to save room for weapons on the other ships. Gunboats are smaller, turreted craft, similar to modern PT boats, and they play a similar role- point defense support for larger craft in a bigger operation, or running interference when needed. Of course in my current game, my gun "boats" are 7000 tonnes- as big as many destroyers. (Then again, my destroyers are 13,300 tonnes.) All in all, working together, they made Swiss cheese out of several precursor ships, including one with heavy beam armor. And one gunboat took an entire salvo of 7 anti-ship missiles before I realized I'd let them extend their range too far in front of the escort craft. It survived, without taking too much damage.
Of course, back to the original post, I believe in quality and quantity. My carrier group alone has 19 ships plus fighters. Destroyer groups can operate independently of the fleet as a whole, but never have less than four ships- a destroyer, its support escort, and two gunboats. Remember, in the real world, you'll never find ships working alone, either. My carrier groups are modeled after US carrier groups, which have the carrier, a couple destroyers, several smaller communication ships and support craft, and even a submarine or two, plus oilers and supply line craft. The theory is that, if you're a country who's thinking about causing trouble, just seeing that carrier group sitting off your coastline will make you think again. (And carriers are massive. The USS Enterprise is 94,781 tonnes, and 342 meters long. Bigger than the Pentagon.) Anyway, ships that large are often multi-role. The Nimitz-class carriers, besides carrying 90 aircraft, also mount 16-24 surface-to-air missile launchers, and a massive array of sensors, so it carries its own area point defense. Building a multi-role craft like that in Aurora is definitely an end-game proposition. But it still travels with support craft.