[ITSv40]

An interesting question, but I feel difficult to answer unless you can experience two similarly maintained cars driven over the same road to do a direct comparison.

My own car is factory spec and maintained as it should be with the correct tyres inflated to the correct pressures. Comfort suspension with a strut brace fitted. The strut brace did make a difference, but not massively, it went from 'alarming' to 'just having character'.

I do find the road surface has a big impact, where driving on a well maintained dual carriageway it drives tight and without any shake. Turn off onto a potholed country lane and it will shake over rough surfaces.

I do think the geographical location will make a difference. You are in Wales so your roads are built on rock which is stable and you should have good even road surfaces. Here in Northamptonshire we are on clay and the roads do subside and move about with the resulting surface deteriorating and becoming uneven. The hot dry summer of 2022 seems to have had a devasting effect on the substructure of the roads and they have become more uneven than previously.