It may be worthwhile to consider what charging plug type will be available and if there are standard lengths of power cables. For instance, if USB-C (or USB-A) is available, most cables will probably be in the one-or-two-meter length. If 220V is used that might allow for longer cables like 3m. SBB may want to look into combo plugs where USB and 220V are available from the same plug, like some airlines have installed.
I’d prefer not to be in a position where I could trip over a long cable, I have a cable draping over my head, or the device is in an awkward spot because the power plug is in a bad place and/or my cable is too short for safe charging. For me that means I prefer having sockets between or below the seat instead of having sockets on the wall or even at the table (for those of us in an aisle seat).