OK.. I admit.. this one is all my own... but given that I hold to the theory of galactic economics and that Starfleet is of finite size, I had to explain the plethora of starship types that appear in TNG. Really, navies move towards commonality rather than diversity, so it follows that starfleet should concentrate on a few good types rather than a wide variety.

I may have also said this before, but in wartime situations, the normal (OK, historic) reality is you build more of what you have rather than invest needed resources in coming up with new stuff.

So... Howcome all the ship types? It was all really nice and pretty until First Contact came along and dumped four new types on us, none of them looking as if they were mainstream Starfleet ships. So here is my unique take on these:

Akira is one of my GP ships, built to a Federation design dating from the late 2350's. What makes it unique is that it uses a lot of commercial components so that the production does not consume strategic materials, i.e. Galaxy/New Orleans family components. Which does not mean the ship is wimpy by any means... I'd put it up there somewhere past an Excelsior in terms of power and force. I do not subscribe to the idea that Akiras are carriers.

Norway is a limited-run testbed design dating from the early 2360's. They are not front-line ships, as they are constantly "in the shop" reconfiguring with new equipment or "out on the range" testing said equipment. They showed up in First Contact because the action took place close to home, where the Norways are based.

Steamrunner is a mass-fabricated built-on-speculation design dating from the late 2350's. Build by a commercial firm and offered to Starfleet, Steamrunners were at first rejected, but later bought en-masse in the 2360's. They are built on an assembly line owned and operated by a commercial firm. I make them small but powerful.

Sabre is a mass-fabricated design built by the same company as Steamrunner, using a lot of steamrunner components. If you look close, you can see a lot of similarities in the design. For example:

Sabres are small and serve as scouts and light combatants, NOT huge battlecruisers.

Just my .02 cents.