THE WIKI AS SOME GOOD INFO on combat and ship roles.  Generally speaking you want the largest hull possible with the most hitpoints.  small ships are cheap and can be turned out quickly evev from yards with low manufacturing.  This lets you field a large ship count fleet quickly.  he way combat works is basically by rounds and weapon fire rate.  A large cruiser with many guns will only fire on one target / round  resulting in massive overkill one ONE ship at a time. The fleet of smaller ships can pick apart the cruiser.

Combat ship sped (thrusts) let you close the distance to the enemy quicker.  A basic missile ship can get 2-3 rounds off before a kinetic gets into range.  It used to give you a slight defensive boost but i think that has been taken out.

Good input on their possible advantages, thanks.

I sometimes like to build swarms of tiny ships loaded with weapons. I find they are effective against planet defenders and when I want to keep my larger ships intact for possible returning defending fleets.

I've been trying to figure out the usefulness of a guardian type ship.  For example, if I built a ship that was purely focused on defense and set it as a guardian will the AI actually target it since it has zero weapons and threat, just because it is a guardian?

Again, my mod (I should really upload this) gets around this by making sure capital ships are prioritised by both escorts and assault ships. If no capital exists then assaults will target escorts and escorts will target assaults, leaving support, interceptor and guardians as the last ships they target. In this way ship combat isn't as exploitative unless you alter your ship class in the editor (which I personally feel is an exploitative mechanic).

What do you mean when you say their target prioritization system can't handle it?

Smaller ships can be a little cheaper to build, but the cost of engines, weapons and shields will make a good small ship almost as expensive as a good medium. The real difference is that a small ship can take a smaller number of damage points before dying.

Generally I focus on improving my medium ships and cranking out a decent number of them, then researching logistics techs so I can put a lot of them in one fleet.

After I research carrier techs I move to large hulls. I've never really needed to go on to huge hulls, but if I'm far ahead on research I build some huge carriers.

again thanks for sharing this

in your opinion what would be the more fair and handicapped way to play if you do not do what you suggest which is pump out escorts full of armor and no weapons with, capitals covered up in weapons and 0 armor

If they allowed more than 1 shipyard per planet small ships would be really good.

But, they dont, so...

Larger hulls are sufficiently advantaged in potential strategic mobility relative to smaller hulls that I consider it unlikely that you'd be able to get enough smaller hulls to make up the difference. A ship built on a Huge hull, for example, can be as fast as the fastest possible ship built on a Large hull while still having 50% better attack and defense scores than the most powerful possible ship built on a Large hull which uses similar weapon and defense component ratios. A ship built on a Large hull that spends a Small hull's worth of capacity on hyperdrive components has the same strategic speed as a ship built on a Medium hull which spent the same amount of capacity on hyperdrive components, and the Large-hulled ship is about twice as powerful as the Medium-hulled ship, assuming both are built as warships with similar weapon/defense components and component ratios.

Moreover, especially later in the game, the hull manufacturing and especially maintenance costs become increasingly negligible by comparison to total ship manufacturing and maintenance costs, so the cost of a ship built on one hull class relative to the cost of a similar ship built on a different hull class is similar to the capacity ratio of the two hull classes. This would suggest that a Huge-hulled ship costs roughly as much as ten Tiny-hulled ships. A single Huge-hulled ship can have five times the strategic speed of the fastest possible Tiny-hulled ship while still having about five times the attack and defense scores (~= notional power) of the most powerful possible Tiny-hulled ship designed with similar weapon:defense component ratios. If the Tiny-hulled ships being compared to the Huge-hulled ship have exactly half the speed and power of the fastest possible and most powerful possible Tiny-hulled designs, that single Huge-hulled ship offers the same total number of actions per turn and ten times the notional power available per action as all ten of the Tiny-hulled ships you could get for a similar cost (assuming the Tiny-hulled ships are all operating independently; if you begin collecting the Tiny-hulled ships into fleets, the Huge-hulled ship gains more and more of an advantage in actions per turn and will never have less than parity in notional power per action). The Large-hulled ship described in the first paragraph only costs ~33% more than the Medium-hulled ship while having twice the power per action and the same total number of actions per turn.

Arguably, the smaller ships have an advantage in their higher tactical speed, but due to how battle resolution works higher tactical speeds are as often a disadvantage as an advantage. Arguably, the smaller ships have an advantage in the number of opponents that they can target per round, but larger ships can more or less make up the difference with a carrier module or two and often don't need to sacrifice that much for them.

End result is that there really isn't that much going for the smaller hull sizes under current mechanics unless you're in a situation where you don't have the economy to pump out the bigger ships at a reasonable rate (producing additional scouts for initial exploration can be an example, if you're unwilling to rush Cargo-hulled scouts and don't want to use construction or colony ships as scouts; using turn-0 tech, a Cargo-hulled scout costs about as much as three Tiny-hulled scouts to produce and the Tiny-hulled scouts reveal about as many tiles per turn, and depending on the map layout having more slow ships with short sensor ranges can be better than having fewer faster ships with larger sensor ranges, at least for a while).

I did this in one of my games once. Tiny hulls combined with the Hyperion Logistics allowed me to pack 64 well balanced ships around a planet for defense. That fleet destroyed several huge ship fleets with logistics at 60. And, it wasn't hard to replace any of the defending ships, if any were lost.