I like both colors, but it seems to me that there are a lot more orange ones than yellow ones. Also, everyone seems to be buying the new Challengers in orange too, so I think the yellow will just stand out a little more.
As far as the motor, you really have to decide what you want to do with the car. If you are going to take it to the track, flog the crap out of it, or are just looking for "WOW factor" at the car shows, then go with the 440+6. But if you are not interested in gobs of torque, and just want something nice to show, an original numbers matching car would be a lot cheaper and more authentic. Both motors will make your car do 65, the 440 will just get there a little quicker.