Frankly, the whole set of historical ship-class titles is probably inappropriate for space combat games. They generally fail to be usefully descriptive even now. Most started out describing some type of sail-powered ships (not even always warships) and, over the course of a few centuries, most have been applied to ships of countless designs, intended roles, actual roles, actual armaments, sizes, and displacements, and relative sizes, armaments, and displacements.
If you were going to stick to classic terminology, you'd probably want to use about 5 terms:
Destroyer: small warships intended as escorts and scouts, either for mercantile convoys or military fleets.
Cruiser: larger warships intended for long-term, long-range deployment. These tend to be fairly fast, intended to engage other cruisers and frigates (either offensively or in protection of civilian convoys) provide intelligence and local military presence, and to participate in proper fleet battles as support and escort as needed.
Battleship: large warships intended for decisive fleet-on-fleet actions. Ships of the wall, these are designed to fight other battleships large-scale engagements. They aren't intended for extended deployments, scouting, convoy protection, or convoy raiding. They are really only there to counter enemy battleships, and are expected to ruin anything smaller than a battleship without contest.
Carrier: A large warship intended to carry small craft.
Escort carrier: a small carrier intended to function in the role of a destroyer, but with a significant complement of small craft.
What about the other terms?
Frigate and Corvette are virtually identical to Destroyer in modern usage. Historically, Corvettes tended to be smaller than frigates, but (aside from those ships which were called frigates but which were actually proper ships-of-the line) were intended for virtually identical roles. Neither describes a class of ships which is functionally distinct from the destroyer, though either term would be an acceptable replacement.
Armored cruiser and heavy cruiser are both terms for describing larger and larger types of cruisers. Essentially, they result from a 19th century arms race among European naval powers who wanted to make sure that their cruisers would have an edge over everyone else's cruisers. Armored cruisers and heavy cruisers are not functionally distinct from cruisers, they're just sub-classes which denote size and armament relative to other cruisers.
The term battle cruiser refers to what was essentially a failure of British ship design just prior to the first world war. British Admiral Jackie Fisher came up with the notion that a large cruiser, designed to outrun other cruisers while carrying battle-ship sized guns, would be a worthwhile addition to the British naval lineup--largely because, in addition to being decisive in cruiser engagements, they would essentially be able to participate in "proper" battleship engagements more or less as if they were battleships. A few other countries turned out battle cruiser designs, but the fad was fairly short-lived--their performance in battle-ship engagements during WWI demonstrated massive shortcomings (most notably a critical lack of armor.) The term battle cruiser refers to a ship intended to serve as both a battleship and a cruiser, as needed. This term is somewhat redundant with both cruiser and battleship, but might warrant inclusion if there really are ships whose design roles fit into this dual category.
The term Dreadnought refers to battleships which mount only big-gun armaments, as opposed to the battleships of the 1800s which tended to mount one or two large-caliber turrets in addition to secondary and tertiary batteries of smaller guns. The design of the HMS Dreadnought design was so successful and so influential that virtually every subsequent battleship was designed the same way. As a result, the term quickly became obsolete, and it is now functionally synonymous with the term battleship.
Personally, I think that it would be better to just scrap this type of terminology altogether, because most of it has been used to refer to so many different types of ship (fictional and actual) that they have been rendered almost dis-functionally vague. I would propose an alternate structure, instead. It would include two basic classes and some number of role-specific subclasses:
Warship: A primary combat vessel--ship of the line. Essentially, a battleship as described earlier. A subclass of warship would be:
- fleet carrier: a primary combat vessel relying substantially on small craft for armament.
Limited Warship: A secondary combat vessel, distinguished from warships either by being intended for a specific and limited role or by being substantially smaller or less capable than primary warships within the same fleet line-up. Some subclasses of Limited Warship would be:
- escort carrier
- artillery support
If I were to go and start splitting up B5 ships into categories, then, I would do it like this:
EA Poseidon (Fleet Carrier)
ISA White Star Carrier (Fleet Carrier)
Shadow Scout (scout)
Vree Xeel (escort carrier)
Centauri Balvarin (escort carrier)
Vree Vaarl (scout)
Centauri Vorchan (gunship)
Vree Xixx (artillery support)