At least in Germany WiFi sucks and is not available everywhere – and even if it is you have to be lucky and actually be in a train that supports it. In general seats are most definitely more comfortable in longer distance trains. Yeah, you can find a seat that’s less comfortable in a long distance train than in a regional train, sure, but that’s hardly the point, is it?!
And electrical outlets are getting more common, sure, but the vast majority of German regional trains does not have them and you can only be certain that there will one in a high speed train.
You said it may differ elsewhere — I was providing a more general view of what I would expect in Europe.
WiFi varies a lot from country to country — some places you're lucky to get it on any train, others it's becoming coming common on even regional trains; seats on a lot of the older ICE2 sets were really quite terrible prior to their recent refurbishment, and a lot of IC trains in Germany had far better seats; electrical outlets differ from place to place — the TGV Duplex will never have power outlets at all seats, for example, despite being a high speed train, as there simply isn't sufficient power spare to provide them, and as another example in the UK it depends far more on rolling stock age (or refurbishment date) than whether it's a long-distance train or not.
At least in Germany WiFi sucks and is not available everywhere – and even if it is you have to be lucky and actually be in a train that supports it. In general seats are most definitely more comfortable in longer distance trains. Yeah, you can find a seat that’s less comfortable in a long distance train than in a regional train, sure, but that’s hardly the point, is it?!
And electrical outlets are getting more common, sure, but the vast majority of German regional trains does not have them and you can only be certain that there will one in a high speed train.