If you are on the fence about PASM and money is not a huge deciding factor just do it! I have a 987S with PASM and 19's, but have driven a 987S without PASM as well. Here are my thoughts.

1) PASM in normal mode gives a much more compliant ride over rough surfaces than the standard suspension. There is no question in my mind about this. Your wife or girlfriend will thank you for having this option when they are not being jarred over rough pavement.

2) PASM in sport mode with the 19's feels noticeably more agressive than the standard suspension. The ride can be a bit jarring over rough pavement, but on smooth twisty roads it is pure heaven.

3) PASM equipped cars ride slightly lower than than cars with the standard suspension. This reduces the gap between the fender and the tires. While this is a cosmetic reason, it is still one to consider.

4) Finally, the ability to change your suspension settings is just so damn cool!

One final thought, I would make sure to combine PASM with the Sport Chrono. The more aggressive throttle settings in sport mode and the tighter suspension turn the car into a different animal when really pushing it.