¿First Class vs Normal Pass?

Hola/Hello,

I'm planing to travel with my wife this November from the 12th to the 29th (16 days without traveling days). Can you help me please in deciding which pass to buy (14 or 21 days) and if you really, really... really recommend First Class? because sometimes this kind of passes don't apply in some trains or there are no availability. Are this seats very comfortable? The longest route we're doing are Kyoto-Fukuoka or Kyoto-Hiroshima and Okayama-Matsuyama (and back) so I don't think we need a First Class to sleep or be more comfortable.

I really appreciate your recommendation.

Arigato! Gracias! Thanks!

P.S. I'll arrive and depart to/from Narita.