As a two player game, it ISN'T about skill, as the game is programmed to "speed up" the people who are behind to make the game closer. This is especially evident on the beginner course. On the Advanced and Expert courses, however, speeding up the car CAN'T help a bad driver ENOUGH to bring them up to speed with someone who is experienced with the game. Unfortunately, in a multi-player daytona game, it is almost ALWAYS the beginner course that people select. This "feature" can be disabled by holding down a specific button while selecting the course (do a google search for daytona arcade "tricks"), but more than half of those playing must select this in order for it to take effect.
As a single player game, it is much more challenging and satisfying to play the "expert" course. The "Beginner" course is even fun. If you have guests over when you are playing, go for the twin. If you are buying it for yourself, and you don't have people over very often, don't worry about getting a single. Also, Daytona 2 is set up to be used as a single easier than the original game. There were a lot less "single" original Daytonas made, although they ARE out there.
I have had some issues keeping one of my two Daytonas running. The first time it was the main CPU board. The second time it was another board. I think it was the sound board. Right now, my player 2 side isn't working. I checked the power supply and that's not it. It probably is in the CPU board again. Luckily, I have a friend with a spare boardset, and when we get around to it, we will get it back up and running.
In my opinion, the original Daytona USA IS one of, if not the BEST racers ever made. It has been so successful in fact, that Sega is re-releasing a slightly updated (graphically) version of the game called Sega Racing Classic. SO, if you have deep pockets, you can buy a NEW ONE next month...
http://www.youtube.com/watch?v=PAN1IVXSsk4