According to one of the other drivers who has asphalt experience, the dirt is a whole lot more challenging and fun. He has a tach and lap timer in his car which he looks at regularly on asphalt. He said he has not looked at it once while on the dirt. Too busy!!! I have only run them on dirt so I cant compare. This driver that I am talking about owns Rusty's old Legend car.
The only problem with the Legends on dirt is if the track gets rough they are a handfull and usually see a lot of ball joints broken.