The X260 XF diesel (2015 on) uses either the 2.0 ingenium engine or the 3.0 V6, whereas the earlier X250 model (up to 2015) uses either the 2.2 or 3.0 V6 diesel engine.
The 2.0 ingenium engine doesn't have a brilliant reputation for reliability unfortunately.
General opinion is that the X260 also had lower quality interior materials, until the final facelift in late 2019, when it got the interior upgrade that it deserved.
Personally, I would look for one of the last X250 3.0 V6 S Portfolio models, very well specced and great interior quality.