I would prefer an at-seat service if it:
1. Offered a decent range including proper quality hot drinks. Tea is harder to do wrong (though I was pleased to see it's Yorkshire on LNER), but for coffee instant, even fancy instant, doesn't cut it. DB have for years brewed filter coffee off the train and carried on a flask of it which works, or alternatively so do those filter cups Ryanair and TPE use.
2. Had enough stock on board.
3. Was near-always there, and was reliably on the PIS as not present if it wasn't going to be present.
4. Was on a train which was adequately not overcrowded that it can always get through.
5. There were enough trolleys for a reasonably frequent pass-through - certainly not just one on a 10 car train (yes, you, SWR).
However, in most cases none of these are delivered, so a buffet wins out.
