From what I've read, the 2.6 was a big improvement on the 2.5? Almost on par with the mk1 omega 3.0?
I'd say there was no significant difference between a 2.6 and 2.5. Except that the 2.6 seems to have the most trouble of the lot of them - MAF sensors failing, valve stem seals, etc.
That bodes well then😋
It depends on the date of manufacture, really. Around 2001, I believe, there was a batch of dodgy valve stem seals that were used on the 2.6 engine and they didn't seem to find their way onto the 3.2s of that period. Most engines with these may well have done enough miles to have exhibited the problem and been fixed by now. Haven't seen one on here for a few years.
The MAF sensor is identical to that used on the 3.2, but something about the way the 2.6 is mapped makes it much more sensitive to ageing of the sensor, meaning we see more problems on the 2.6.
In all other respects, it's an identical engine, save for different bore and stroke, and sodium filled exhaust valves on the 3.2.