This is a question that I often get from people looking at the selection of bikes, so here's a summary of the 3 models.
Special: The Special is the traditionalist's choice, due to the craftsmanship of the lugged and brazed frame. The road manners are incredible- it feels very connected to the pavement, very secure, especially on rough sections. This bike soaks up road vibration, and is, in my opinion, the best one for long distance riding comfort.
Lightning: The Lightning is the choice of weight conscious riders. While it won't soak up road shock as well as the other 2 bikes, it is superior to virtually any other aluminum frame out there, due to the thinner walled, round section tubing (possible with the addition of the element scandium to the alloy) and the road type frame design. Also, many of the aluminum frames use aero or teardrop section down tubes which increases the weight, and adds to the rough ride characteristic that alu frames are known for. The Lightning is the best of the 3 for acceleration and hill climbing, due to the low frame weight and the rigidity of the bottom bracket area of the frame.
Classic: The Classic offers what you would expect from a high quality steel frame- very solid road feel and great vibration absorption. It's a great climbing bike and excellent for longer rides.
In summary, it's not really a good/better/best thing, it's more a question of what you're looking for in the ride or the aesthetics. All 3 bikes are a joy to ride.