Help with photography/new camera

[jpgranone]

Hello,

I am looking to get more serious about taking pictures at my home track. Right now I use a Nikon Coolpix 4200. It worked for the fun photos of my friends. There are some wonderful photographers on this Forum so I figured I would ask for help. So having no real knowledge of cameras, what would people recommend? I was looking at the Nikon D300 or the Canon 50D. Please help.