.. except that, when the custard flies furiously at 0-dark-30, and the two guys/gals up front are working their little hearts out trying not to die ... gee but it is nice to have a competent third seat ..
(a) to look after the boiler room
(b) (presuming the company thrust is for basic operational competence as well) keep a relaxed eye on what is going on up front.
I can recall two events where (b) probably avoided a heightened level of anxiety, embarrassment ... or worse ...
Having said that, I have no problem with a two-crew operation .. the 737 works real fine .. but you do need to have two experienced and competent folk to make up for not having (b) ...
I am not at all terribly sure that the present trend to very low total experience in the RHS (which can put the LHS in a defacto SP operation if the workload really ramps up) is a sound equivalent ... as in, when it works well, two crew is great .. but, if it falls in a heap ... it can do so big time ..