I have a 912E, a 968 Coupe, and a 911 (996) Coupe. All three provide a rewarding experience, but in very different ways.
For me, the 968 excels as a commuter car, with its large gas tank (nearly 20 gallons) and good gas mileage. The seats are comfortable, and the 6-speed, 236hp powertrain provide easy high-speed cruising capability at reasonable rpms. The relative rarity of the car makes it special, especially at club events.
The 912E is primitive compared to Porsche's newer cars....it's noisy, it's slow (86hp), and it sounds very much like the VW-derived air-cooled engine that it is, in the best tradition of Porsche's original 356 and earlier 912 models. Extracting the most from this car's engine, suspension, brakes, and steering requires skillful driving, and that's what makes it so much fun. More often though, I tend to drive it in a leisurely fashion because that seems to suit a car of its age. It's somewhat rare (only 2,099 sold in its one year on the market - 1976) and so the car is quite unique, if not particularly valued, among Porsche owners.
The 911 isn't just a supreme achievement in the development of Porsche's rear engine concept, it's an awesome performance car in every way. Perhaps to its detriment, it's a bit too refined in the areas of noise, ride, vibration, and harshness. That's not a complaint, but if you're looking for more of the "raw, classic sports car experience" with an abundance of those sensory inputs, then this car (at least in coupe form) may seem more like a touring car rather than a sports car. But boy, does it perform!!
My next Porsche could be the upcoming Cayman (not the current Cayman S). The mid-engine layout is appealing, but the cockpit seems more confining. And I'd miss the wonderful, sensual shape of the 911 if I let it go. On second thought, I'll keep the 911.