Will get a new 997TT Tip (or its successor iterations) every yr, no matter the N-ring time.

Not an aspiring racecar driver, but do appreciate 50-120MPH accel and steering/chassis/brake feel, esp in twisties; have zero interest in risk/reward proposition inherent in any track-driving.
Am curious re: incremental impacts of hp, torque band, Tip vs manual, trac, chassis, brakes, etc vs N-ring times.....despite much pseudo-precision re: SportAuto times (or whatever times one trusts), my simplistic view is purported time diffces are within roughly 5% for cars ranging from SL65 to 997TT....and we don't have precise supporting data re: individual car test conds: variance of times of same driver/same day/same car; mileage on car; tire brand/tire cond; clutch cond.; brakes cond; etc etc....lots of slop/unknowns in nos. Given how close the purported nos. are and how much slop/unknown is in the nos., IMO qualitative first-hand driving feel of car on one's favorite roads is the deciding factor....

My simple prelim conclusion (gotta place bets early as need to spec cars now to get them anytime soon): no car on planet will offer mid-range accel; trac; steering/chassis/brake feel; and active/passive safety of 997TT Tip for everyday/all-weather use.....and despite prob slower N-ring times, 599 will offer interesting complementary characteristics on dry surfaces...w/prob great exhaust note; ample stgt-line torque; fast F1 tranny shifts w/more ergonomic paddle shifters (vs P's ergonomically worthless Tip buttons); F's latest susp/stab ctrl tech; and a large fuel tank and range, so less freq fuel stops than w/997TT (a major weakness of 997TT for commuting duty)...
So, just need to get both 997TT and 599....at least in US, easy to obtain an early bespoke-spec copy of 997TT; however, 599 will take a bit more lobbying to get an early bespoke-spec copy....