Cats are "air entrapment" hulls. As you pick up speed the air gets trapped under the hull and lifts the boat out of the water. The less boat in the water the faster it will go. They also corner flatter than a V hull. They usually don't have cabins and insurance is very high on them. My buddy (who owns a 38 Cig Top Gun) just told me about another buddy thats getting a 42' Skater with 1400 HP Zuls. Said insurance is going to be $28K a year! Could be BS but that is a big $ boat.
I don't think there is any additional maint issues for twins besides what you said, 2 of everything. I went from a single Baja Outlaw to a twin Cigarette and costs certainly do go up. Oil, gas, any accy changes, etc. just multiply by 2! Also bigger boat = bigger trailer, more weight, bigger tow vehicle, more gas to pull it, more insurance, etc.
Twins make docking easier though. Just twin stick it, hands off the wheel.