I used nutplates on mine. It gives you more options and improved access for maintenance but takes time to instal and costs a bit more.
I put my strobe pack under one side and my comm aerial under the other. I also ran my flap position wiring under there. Of course I also have ready access to my steps (which have a bad historical record for cracking).
Either way, it's not a make or break decision. I generally find that the guys who get their jollies from building are more inclined to use nutplates, and the guys who just want to get into the air tend to use rivets.
But if you opt for nutplates don't take the advice of installing one at every second rivet hole. I doubt that would be structurally adequate.