So performance wise whats the differences, I'm posting this in both the X308 and X350 threads so we don't get a set of unfair opinions.

But it's always been an argument between the two owners, which is quicker and what's more important, by how much?

The facts=
X308 XJR 370BHP and 382 LBFT @ 1837KG's = 205BHP per tonne, 5.3 to 60mph.

X350 XJR 400BHP and 408 LBFT @ 1665Kg's = 245BHP per tonne, 5.0 to 60mph.

So it looks as though the X350 has the lead, but does it?
What are your experiences, have you ever raced on the road or a drag strip, if so I'd like to know the outcome.

Personally I've owned both, though never raced them both head to head, but in my opinion I feel the lighter X350 has the edge on the kickdown with the better tranmission, it seems to get up and go quicker, but by how much I don't know.

 

I thought the X350 XJR was 390 bhp.

 

It's really comparing apples to oranges. Hp to weight ratio is obvious the 350/358 has along with better technology for the most part. Two things the 308 has advantage over the 350/358 is a more robust suspension
(not necessarily more comfortable or better handling, just not as many bushings that wear out) and a classic look. Other than those two advantages, I'd love to have a 4.2 S/C along with a 6 speed ZF trans in my 98 XJR.

 

Weight difference is 110kg, 1735kg vs 1845kg . 1665kg for X350 XJR is dry weight. Same for X308: 1775kg.