In C# Aurora it is the same support needed for one 15kt ship as it is 3 5kt ships.
An understandable but erroneous conclusion.
While there's a much smaller gap between the logistical pressures between a large ship and a fleet of the same total weight of smaller ships, it's there. 3 5kt ships can effectively be fielded with only 5 kt in maintenance capacity, with 1 in overhaul, 1 in transit and 1 doing whatever useful thing you want to use the ships for. This is in contrast to the single 15kt ship with the same level of maintenance facilities, which is more or less stuck in overhaul or running out its maintenance clock, suffering ever escalating demands on MSP and other logistical support.
When it comes to designing and building a force you can field, you can't design and build a force meant to be 3 times or more larger than your maintenance capacity unless that force is effectively not meant to come home to be overhauled and maintained.
You can actually do that, with ships designed with a maintenance lifetime of a decade or more that are never upgraded, only scrapped and replaced. This is generally what you do with military stations anyway. But most fleets aren't designed with this level of disposability in mind, so most fleets are going to need more than 1/3rd of the total fleet weight in maintenance capacity, and depending on many factors, possibly substantially more.
Although, for garrison duty I would never use large ships at all... small FAC or fighters are far more effective for that in general anyway because you are operating from a secure power base and not roaming the stars where you need both range and comfort for the crew.
Changes in sensor mechanics make smallcraft swarms less viable due to being detected earlier. They're decent PPV for their weight and highly modular in deployment numbers though, which makes it easier to tailor to the colony's PPV demands.
If you have the infrastructure and yards you would in general want one super big ship at 100kt rather than 10 10kt ships, but that is rarely possible in practical terms... the drawback is of course that one ship can only be at one place at a time where 10 ships are way more flexible. But in a showdown one big ship is almost always going to be more powerful. This then obviously come at a price of needing more resources to build up the infrastructure and time for such a fleet to grow and mature. This is why it is wise to invest in both small, medium and large ships in general. It is not stupid or unwise to use smaller ships and neither is it stupid to build large space hulk like ships either. It all depends on the conditions.
Spinal mounts and Particle Lances do not turn ships of substantially smaller size than their target into the capital ship murderers that are VB6 meson/microwave smallcraft swarms, but it does make them a rather credible threat, especially against early armour dependent ships. The particle lance's ability to burn through en entire armour column to spend all of its remaining power on internal damage is not to be underestimated. Shields change the equation considerably however; shock damage aside, they're effectively an armour column as large as the total rating of the shield. That doesn't help much against missiles, which tend to wash over the armour layers and wear them away anyway, but against something that has good piercing against thick armour has more trouble with that.
And those 10 10kt ships get ten shots per round until a ship is forced to disengage, while the 100kt ships probably only gets 1 shot per round, if it has a spinal weapon.
