I've raced both and in my opinion a 4 speed is cheaper to maintain and more fun. You don't have to go super expensive with either but to get the most out of an automatic it is gonna cost you more.With that said I suppose it is because I can do my own 4 speed tranny work and had to pay to have my auto built.My setup was purchased new years ago when things were a lot cheaper for example: Anson scattersheild with block plate new was only $175.00
My tranny was new from Ma Mopar and only $375 (A833 short tail shaft) and my shifter is a Hurst Verti-gate inline shifter for $125.00 with reinforced shift rods(called monster rods back then) the flywheel is a recent purchase for $100 from 440 source and the clutch is a 3800# Zoom setup that I bought and never used till now for $150-160.