If your aim is to go fast, easily, with maximum safety & comfort then a newer Porsche is an obvious choice.
Old Porsche's are still fast cars but require far more effort to manage and extract the results out of - that's exactly what creates the charm and driving satisfaction. I'm more interested in the raw driving experience than the conveniences of a modern car, hence why I'm drawn to the older cars. Yes, modern cars are easier to drive & live with but ironically that's what makes the experience less exciting or rewarding for myself.
I had a 964 as a daily for almost 3 years (and aside from the turning circle) loved every minute of it. I'm quite happy in a manual as a daily (always) and I'm currently using my LHD 65 as a daily now since I sold my last DD. I'm, actually struggling to justify buying a newer car as a DD as I'm really enjoying cruising around in the 912, makes every journey a novelty. I am well aware that I'm in the minority though.....................I enjoy suffering and tolerating an older car as it also saves me a gym membership.
New cars are fantastic, they do everything so well. In terms of "sports" cars the fact that they do everything so well is actually the issue seeing as you will barely be able to push the car to 5/10's on a public road. GT4, GT3's etc. are great but unless you hit the track or are prepared to roll the dice on a public road you'll rarely get to experience their capabilities. Accessing the capability of an older car is far easier (at lower speeds) and is no less fun (fact!)
So, the decision really comes down to how hard you want to work for the drive. Understandably cars like a 996 are a great happy medium and to me either side of these you start swapping out comforts/sophistication for a more "basic" driving experience/package. Sure, driving around in an old air cooled Porsche looks cool but the sweat stain on your back maybe your downfall. On the plus side massive biceps maybe possible from the lack of power steering (or in my case actually having to wind your windows down manually!) but again you have to be able to accept the inconveniences - driving and relying on old cars daily isn't for everyone but I'll happily do it.