I've owned a Classic '50s P for several years. I think I found it used in '09. In '08 I bought an American Standard P. The Am. Std. was very good, but I actually preferred the tone on my Classic '50s, and ended up selling the Am. Std.. I think tonally, you'll be happy with either.
From a COMFORT factor, I preferred the neck on the Am. Std. over the '50s Classic. That's mainly because the width at the nut on the Am. Std. P is 1.625", whereas on the Classic, it's 1.75". A lot of people actually prefer the wider width, but I don't. Not a huge difference, just a slight preference. Plus, the back of the neck on the Am. Std. is satiny, while the Classic '50s is glossy. But tonally, I love the Classic '50s.
Although I don't own one, I have also played the Road Worn P's (and J's), and they have probably the most comfortable necks of all. Plus, they sound awesome as well. If the roadworn look isn't a turnoff for you, you might want to check them out as well.