Currently technology has the most powerful single fleet buff in T4L: 20% increase to capacity and venting is extremely large. On an Eagle for example is the equivalent of 10 caps and 10 vents for example. Special modifications is a buff to non-story point ships, but without more OP from free hullmods most ships can't truly take advantage of 10 extra vents, so I'd say special modifications is primarily a big buff for story point ships only (and costs a lot of them of course).
Weapon Drills, Crew Training, and then 20% speed either from Coordinated Maneuvers or built in nav relays on enough ships gives a 25% speed buff, +10% damage (at 180 fleet size), 5% less damage taken, and the other benefits of 85% CR to all ships, which is really not bad.