spark plugs

I have an 08 Pitbull with about 10k and it seems to foul plugs yearly. I store it in my garage on a digital tender with the fuel off. I have been using the Champion RA8HC. is this correct or is the RN12YC better? do the spark plug wires need replaced? thoughts? thanks people. R

pulled these two pluugs fron my 2007 kg with an S&S 117 cid engine. It ran really good and was time for its 5000 mile service. Upon inspection Ifound a different pattern of wear. Anybody want to express an opion of why the difference? The plug on the left was in the front cylinder.