Clearly, if it must be a soot chucker, the V6 diesel is the one to have. Actually, the V6 -S badged ones.
The non S V6 soot chucker is 235ish bhp
The S V6 soot chucker is 275ish bhp (up to about 2016ish, when it became 300)
Tax is the same, claimed economy is the same. Why would anyone buy the half-arsed one? The more powerful one has 600Nm of torque as well, which will rip the tarmac from the road.
This is the problem, the only XF you can buy in my view is the XF-S. I sat in a few of the latest shapes XF's but the lower spec R-Sport or 2.0 ones did not have much adjustment in the seats, no electrical tilt.
The XF-S has more adjustment in the seats (no doubt an option on others) but makes it harder to find examples.
You need to spend £17-20k ish to get something half decent.
The seats in the SRi Mummy bus (MV6 cloth style) were far more supportive than any of the Jaaaags.