Are you a Jag owner? If not, explaining it to you won't make you understand. If you need info pick up some automotive magazines orjust surf on line.

 

the "last" of the s types was a very reliable car just the early s had a lot of problems.. .. now the XF is aawesome car.. electronically is totally different..then the "s" the XF is pretty much a XK just in 4 door sedan and the body underneath is a "S". same suspension.. as the last s type 2007-08 ....

 

i just traded in my '02 S for a '09 XF SC .. I loved my S, and after 6 years it was in perfect "mint" condition.. However, once I sat in an XF at the dealer, I (and my wife) could see that it was in a whole 'nother class than the S .. My wife was never overly impressed with my S - but she loves the XF and is now jealous (she drives an '06 Infinity M35)

The XF is has a much better fit and finish/build-quality. the power of the SC is incredible and blows away the S (and most other cars) - even the non SC, PremLux blows away the S.

IMHO, unless price is a factor, get the XF..

 

We traded our '05 STR for the XF S/C in spring. It was the first one off the truck at our dealer. They called and said they had one in if we wanted to test drive. After driving the XF we knew we had to have it. Don't get me wrong, the STR is an excellent car and turned heads wherever we went but we like the XF much more.
As far as reliability concerns, I wouldn't worry. I heard the same thing before webought the STR (especially from the Mercedes and BMW dealers) but we never had a problem with it other than an allignmentissue that ruined the front tires. I can't say for sure it was a dealer/mfg issue though.
The XF has slightly more power than the STR had but it feels like a lot more in Sport mode. Either one will spank a lot of unsuspecting "stoplight dragracers".
We also had a '05 CTS-V that we sold last year. In my opinion either Jag is a much better road car. IfI were going to track it on weekends the V would probably be a better bet. I'm still waiting for the '09 V to see how it compares.
One thing that I would like to see improved on the XF is throttle response in the "normal" mode. I think the point is to give it a more luxurious feel but in my opinion it has too much lag, almost like the torque converter has too high a stall speed. That probably isn't at all what's happening, but it has that same type of sensation.

 

I have an 04 S Type V8 and just bought the XF SC. We drive them both.
S has been very comfortable and reliable with over 30k miles. Suspension is way too soft though and J shifter is a bit out of date.
XF SC is a whole different thing: way more power, transmission with two modes and paddles, sports driving mode (CATS?), etc.
The XF SC with the transmission set to S and the "racing flag" button engaged is a pleasure to drive even without using the paddles; unlike most autos, it's always in the right gear, downshifting as speed drops and vice versa. Pretty sure this is the same 6 speed ZF unit I had in a Bentley GT.

 

AFAIK, there are only two six-speed RWD automatics: ZF's and GM's.

The one in the Bentley, like in all BMWs, would be the ZF unit. But in any VW application, it'll be a little different, since it must be packaged for what's essentially a longitudinal FWD powertrain with AWD added on.