OK so your brother didn't like Cardiff to Nottingham on a Turbostar- however as i said up-thread very few people will be asked to make journeys of over 3 hours like your brothers without alternatives. And remember just how many people are making 3 hour plus journeys internally on Wales and Borders?
Why the 3hr threshold? Why should pepole making 2 hour journeys such as Aberystwyth to Shrewsbury suffer reduced quality trains? London Waterloo to Portsmouth Harbour is under two hours on a fast service and I agree with the plan to replace 450s on those services with 5-WES (Wessex Electric) units. Admittedly in that case it is not only the door arangement to compain about (2+3 seating and 20m versus 23m vehicles will be having an impact too), but I still feel that if a service does not need to stop frequently at busy stations then trains should be optimised for comfort and that means the 5-WES units (or 444s) are more appropriate in that case.
The way I look at it is more how many pepole are making very short journeys of only 5-10 minutes, particularly where this demand is 'peaky', versus the number of pepole making relatively long journeys (anything from about 1 hour upwards is 'relatively long' in this context). Borth to Machynlleth, Machynlleth to Caersws, Newtown to Welshpool and Welshpool to Shrewsbury are all sufficiently long gaps between stations that I don't think you should be expecting pepole to stand (I've not counted Dovey Junction as very few, if any, will be starting/finishing a journey there). Thus the wide doors would be taking away furnishable space for no reason. True, stations on the Cambrian coast are much closer together but many of them are request stops with relatively light use and are unlikely to cause a dwell time issue* (and in many cases a fair proportion of passengers using them are likely to be going some distance rather than just to the next stop, unlike on a city metro network).
* or, if it did, it would be due to local-door operation at a short platform rather than the design of the train.
QI Klaxon! Correct meaning, but Aberystwyth’s name is misleading – it's actually on the mouth of the river Rheidol. The river Ystwyth (literally, the winding river) is slightly to the south.
Don't they both merge just before flowing out to sea? But yes, the river that flows through most of modern Aberystwyth is the Rheidiol.
I believe krus_aragon is correct, the Rheidol and the Ystwyth meet the sea in almost the same place (whether the Ystwyth actually meets the sea or the Rheidol I'm not entirely sure). I suppose Aberystwyth could equaly have been called Aberrheidiol, but what does the 'Aber' on the ValleyLines relate too? Is it just 'mouth' as in a person's mouth rather than one river following into another?