A 12 car 700 has fewer seats than a 12 car 365.
Seriously, I really don't understand why we can't have the class 700s with 365 style seating. I doubt this would see a significant reduction in capacity.
We do need to remember that the majority of the 700s won't be crush loaded, and the train ambiance should reflect this.
The maximum (safe) capacity of a 12-car class 700 is (ISTR) 1750 passengers of which 666 will be seated. The corresponding capacity of a 12-car Electrostar is about 100 more seats including the centre of three seats which are rarely used in preference to standing and about another 500 standing. I presume that the 365s have a similar capacity. The bottom line of Thameslink line travel including the GN branches in the near future is that trains will be at the maximum length for their routes and with support of the latest technology, running at their maximum workable frequency. All of that is necessary for the expected passenger growth, even with the considerable infrastructure investment that has taken place in the last 10 years.
For off-peak travellers, the 700s will have about 15% less seats, although the loss is actually very little owing to the tendency for centre seats to be ignored by most off-peak passengers. Clearly the same seating has to meet the requirements of all service loading, but the critical core dwell time issues have to take priority. The aspects of design to achieve the core performance have been discussed thoroughly earlier in this thread, specifically, the absence of power outlets, tables and seat armrests. The delays that such facilites in commuter trains contribute to have been studied and AIUI, demonstrated in specific tests, - such is the critical nature of Thameslink core operation.
As for the 'ambience' of various trains, this is to a large degree, a matter of personal opinion, and of course, many passengers will have their own preference. A significant proportion of all passengers though are quite ambivalent to the aesthetics of train interiors and just want to get there with the least time and safety impact. In the case of high capacity commuter trains though, punctuality, journey times, reliability and above all, safety are the most important parameters, particularly when the
average passenger journy times are considered.