Okay, here is what I've seen here, at the CIC, and at the TCE site.
The WC3 ships, minus the Thunderbolt VII, Longbow bomber and Excalibur, are all old. The Arrow and Hellcat V have been around for sometime by the time WC3 rolls around.
Most of the WC2 ships are still in service (during WC3). Some ships, like the Scimitar, are known to have been retired, with a known retirement year. The Broadsword and Crossbow bombers were probably retired, since the Longbow blows both away. The whole Morningstar debate is insane. We can assume that the Morningstar was probably never mass-produced, since there were more cons than pros about it; it had an iffy jump drive, crappy engines and its Mace nuke wasn't exactly "safe."
Perhaps it was rolled out but in limited numbers, like Confed's other problematic "wonder fighter," the Bearcat?
Confed obviously
does have a narrow list of fighters it upgrades and keeps. We see this in the Rapier IIs and the Hellcats and the Arrows.
By WC4, it was decided that, since it was peacetime, that it could save money by cutting back on
a lot of military spending. Therefore, you've got the RIF and a massive "standardization."
Being the tried-and-true, the Hellcats, Arrows, Thuds and Lonbows were probably selected to be kept around. Notice that their weapons are different and more "vanilla;" especially the Thunderbolt VII. Also, Arrows can now cloak. The Excalibur, a proven fighter (one blew up Kilrah, after all) was kept but with massive changes for the cheaper; less missiles and little armor and shielding upgrades. The Excalibur, also, received cloaking.
As for the UBW arsenal, it's pretty freakin' obvious from the get-go that they're economically weaker than the Confederation. In fact, the majority of their wartime fleet came from Confed, no...? At any rate, the UBW is known to fly
Scimitars, which we know to have been retired 20 years earlier! Spacecraft like the Ferrets, Rapiers, Sabres, etc. were probably cast off because there wasn't much you could do with them that couldn't be done with the more cost-effective, easier-to-mass-produce WC3 ships (I know they were designed to meet technology limits but, from a practical standpoint, the WC3 ships are much less complex in design than WC1 & 2 ships and look so much easier to slap together).
The Bearcat, true, was an expensive craft. However, I think of it as the WCU F/A-22 (it even looks like one

). It was designed and began production during peacetime. There wasn't a necessity (at the time) and it was probably started up to get people investing and to create jobs. Of course, unlike the F/A-22, the Bearcat uses a new engine system (like the Morningstar's, is iffy) and is a maintenance pig.
Either way, WC3 ships are older than WC2 ships. WC3 ships stood the test of time and are cheaper. WC2 ships became obsolete at war's end. Border Worlds are poor and can only afford old, tossed Confed materiel.
Take what you want from that... because I think I totally deviated from the point... but, whatever, as this has been debated to death
