I'm 34 and have been doing track days for years. I have met a lot of very friendly and like minded people, some of which I now class as friends. I have managed to blag rides and drives in all sorts of cars from Cosworth engined Westfields, rally cars, through Ferrari's, 750bhp Skylines etc. Through certain contacts I even ended up on a WRC test day at Prodrive's test facility, even drove my car round their test track fitted with all the WRC locators and sattalite emergency systems they installed after McRae's crash a couple of years years ago.
I wouldn't say I'm an expert on the linage and all the different model numbers but....
I've driven a couple of 911's both manual non-turbo's RWD. I've been a passenger in a 911 Turbo on track and a GT2 on road. The GT2 is absolutely awesome.
I have also been a passenger on road and on track in a Tiptronic auto.
The tiptronic is an autobox pure and simple yes it has manual overide but its an autobox with torque converter. IMO it has no place in a 911. It can't be compared to a selespeed or SMG as these are both manual boxes with computer and actuator controlled clutches and gears, they do not have a fluid coupling (Torque Converter). Once a gear is selected both the selespeed and SMG are no different to a manual.
An autobox is good in Jaguars, big BMW's and Merc's, Lexus LS 430's etc. Not a race car for the road.
The manual 911's are all about pin sharp responses and balance, they are an absolute joy to drive on track and on road. The tiptronic is quick yes but the torque converter robs your right foot of that direct connection between engine response and road speed, you can't balance a tiptronic on the throttle it's impossible. This really shows up on track.
The tiptronic is obviously less tiring to drive on road and is a quick grand tourer but if that's what your after don't buy a 911 buy a big V8 auto cruiser like the Holden.
Anyway just my thoughts.