[Cyrien]

Well this is how I use them and it has seemed to work pretty good so far. At least on larger worlds, or small military worlds where I use Cargo Facilities.

Have 3 specialized types of WP or 2 semi-specialized.

With the 3 specialized you want:
--1 type with the longest range weapons you have available. Generally the Missile tech works pretty good for this in the Demo (being the longest range weapons in the demo and all)

--1 type with massive damage decent range weapons. Incinerator and Wave Motion as well as Graviton Hellbores all work nice in this area. This is just some incentive to keep them back.

--1 type with lots and lots of PD cannons. Don't let them just stay outa range and pummel you with missiles if theirs are better than yours. Shoot the things down and force them in closer.

For the semi specialized approach just subtract the pure PD ones and put one or two PDs on the first two types.

This little strategy has normally kept my planets pretty safe... as safe as can be expected with nothing but WP for defense anyways.

Of course no defense will ever stop a truly determined offense. All it takes is time.