It can be much, much bigger. That's not an advantage in all cases, and you can certainly make up for it with multiple ships, but it's hard to say that one giant block of shields is worse than the same size worth of shield components spread over a bunch of smaller ships. Of course, that really goes to the point that the Resupply Ship is potentially more useful acting as a giant battleship/carrier/troop transport than in its intended role, despite sacrificing ~20% of its size to noncombat-related components.
There's also a slight advantage in it being more of a set-and-forget semi-mobile refueling point than the tanker-battleships are, and that the 100 size or so of a long-range scanner component is a rather trivial cost for a ship that can be well over 4000 size (this is more true earlier in the game when the ship sizes are more limited and ~100 size units for a long range scanner plus the static energy cost is a nontrivial addition to any ship that isn't huge or dedicated to carrying the scanner). Going along with the not-yet-late-game tech state, it's also not really a trivial decision to set aside enough space on a warship for refueling purposes if your ship sizes are still smallish, especially if your designs are relatively fuel-hungry.
Resupply ships keep the refueling capability in a single hard-to-destroy target that, if used in the intended role, mostly stays out of fights, while tanker-battleships put the refueling capacity on the warships, reducing the effective size of the warship in question. I don't think that there's any real question that in an equal-tech engagement the tanker-battleships are at a disadvantage against true battleships of similar size, especially if present in similar numbers, but the computer isn't all that likely to put you into that scenario after perhaps the middle of the tech tree. Resupply ships could possibly use a buff, but on the other hand I really think that tanker-battleships would be much less attractive if the computer player was closer to being an equal opponent, especially in the design and fleet utilization departments.
I agree that the biggest benefit of a refueler is how large it can be. You're right in that the larger size gives it some unique applications earlier in the game, before regular ship sizes have gotten larger.
I may not be clear on what I mean by (to use your phrase) a tanker-battleship. What I am talking about is a ship designed to the exact specifications as a normal Refueling Ship design, only set as another ship class (Escort, Destroyer, Frigate, etc). That's it. I'm not talking about tanker fleets anymore, which people didn't seem to like. I'm talking about a single ship in the tanker role that is not a Resupply Ship.
There seems to be two different mindsets here... mine and everyone else's.
My mindset is that a non-Resupply Ship tanker does not have to deploy. It can fill up its tanks with gas in friendly territory, fly that fuel out to a fleet, and dispense it at any location since it does not have to be deployed at a gas giant or cloud to dispense gas, like a Resupply Ship does. A tanker-battleship in this role could easily have zero shields and armor, and no defensive or offensive potential at all. It just flies to the fleet, refuels it, and flies out of the combat zone again. Because collected gas reserves are capped at 30100, you don't need much cargo space on it. If you have the requisite tech level, you can put a gravity well generator on it and some light shielding. This way it can collect as a singleton in enemy territory, and if enemies warp in to attack it, it can fly off unmolested. I prefer this approach because it's more flexible and able to react to enemy presence. Also these ships are built at starbases, so they're easy to produce en masse.
The prevailing mindset, however, seems to be that Resupply ships are the ideal ship class for this role. Because they have a larger chassis, they can mount more shields, making them better able to survive enemy attack. However they are still capped at 30100 gas per type (60200 total), so most of their large space is still free after allocating cargo. They can be a hybrid heavy combat / refueler unit, and if they're caught alone, their higher defenses and potential for offense let them handle themselves well.
Is that about right? I prefer speed and agility and everyone else prefers strength and survivability in a tanker?
I still feel that Resupply ships should have most of the benefits of battleship-tankers. Mainly no deployment time, and the ability to dispense fuel while not stationed at a gas giant/cloud.
< Message edited by Airpower -- 7/6/2014 3:57:15 PM >