Protecting Planets

[Nitram Draw]

I use all three for defense.
The only problem with the WP is space. On a domed planet you can only fit a few medium WP before you run out of space and then you can't build any mines or sats. It's quite a juggling act.
I like mines because even if they don't kill the ship they can come into the battle with damage on them. It's nice when they lose all their shields or weapons before the battle starts.
Using all three options lets me reduce my fleet size. In fact I don't think I have ever exceeded 25 combat ships at one time in any game I have played. I always have more support/colony ships than warships.