I've had a TS, a JTS and a V6 so am well placed to give you a overview of the JTS.
Does not have anything like the character of the TS.
Sounds thrashy at high revs compared to TS (but better than most cars still).
Lumpy at low revs often, not pulling away cleanly.
Tall gearing of 2nd does not allow the extra power to be turned into a quicker 0-60 dash.
You can tell it's got 165bhp compared to TS (150 or 155).
Much better torque curve (i.e. has more low down grunt - mine actually felt like the torque curve of a turbo diesel car when compared back-to-back with my TS).
Better fuel economy (maybe just because I wasn't revving it so much!).
Best thing on PH3 is the lower set drivers seat though (if your tall like me).
I've got a V6 now though which blows both out the water! (except on the twistys!).
Hope this helps.