My view is that, airline style seats maximise the capacity in a carriage where seating is the norm, i.e. long-distance stock.
The standard class carriage of a long-distance train should all consist of airline style seats, with only two tables, one on each side of the carriage where forward and backward facing seats meet. It should also contain a large multi-purpose space, where bikes and luggage can be stored.
In first class carriage, seats should all be 1+2 layout with tables to create the luxury differential compared to standard class (i.e. cattle class).
On a regional train, the seats should stay the same, but the table should be removed in standard class, with a large standing place placed between the forward and the backward-facing seats.
On a suburban train, the majority of seats should be longitudinal seats where maximising standing space should be the first priority, similar to a metro train where there are only longitudinal seats.
In the above, a long-distance train refers to anything longer than approximately 144 km, i.e. starting from London, going further than Southampton, Swindon, Coventry, Corby, Peterborough or Ipswich, while suburban trains refer to trains running within approximately 64 km from a major city centre, i.e. London, Birmingham or Manchester.