I use a crossbow for sneak attacks, a compound bow if I need to fire arrows in a higher rate and for the most part my burning spiked club.
I have a AK47 on my belt for emergencies with a rad remover mod attached to it but I don't like automatic weapons. They are loud, cost a lot of bullets and they are pretty much useless if you want to sneak through a PIO.
But I came to the conclusion that sneaking through a PIO is not the way to go if there are radiated or feral zombies in it. In this case I make so much noise I could outside the PIO to lure the most zombies out of the building and fight them in the open space. And I open up a escape route whenever I can.