[Suicide Junkie]

I figure if I build 10 ultra fast ships, they can move from one battle to another in less time ... ...

Your ships can be as fast as you like, but they still have to travel through warppoints .
I think both ways are probably best. Fast interceptors, and heavy warships each in their own fleets and roles. One plugs warppoints and lays siege to planets, the other picks off anybody who gets past.

Edit: Oh, and doesn't your brother find the mass to propulsion ratio a little low with solar sails? How 'bout a supply ship in each fleet (I'm big into ultra-specialized ships)

The max-tech solar sails are almost as powerful per KT as JP engines. Its not that bad.

As for the supply ship?
My brother's supply ship is a warppoint opener orbiting the cluster of 12 Huge planets in the Hercules system. (As you can tell he's been doing a lot of Stellar Manip )

In case you're wondering;
- Yes, those planets are all in the same sector
- Yes, they are all breathable, Huge oxygen worlds.
- No there is no system type with a stack of huge planets.
- He moved them there using his powerful Stellar Manip techs.
- Yes, he is very powerful, but despite that, I have just bumped into the MEE limit
- No, you cannot borrow my fleet of BattleMoons.