Well, thank you for such a thought-provoking first post here, hornbeam - and welcome to the Coffee Shop forum!
I'm a complete novice myself on Class 166's - but I'm sure some of our other members here will be able to offer explanations on the points you've raised.

Much better than 165 - they have tables in first! In fact I think standard have better table provision thant 165 first!
Other than that - not much else is different - I think 166 have air con and 165 dont - and 166 have carpets - I think.
As first, I will grudgingly do a
PAD» to
WOS» if I a=cna guarantee a 166 - I wont on a 165 - I'd get home an hour later or stay over