Considering a 250nm route with 300 pxd.
Is better a four ATRs (Y-64) or two 737-300 (Y-126).
I just want to know if short routes are better with smallest planes (but with a lot of them) or with a big jet (few of then)
Depends
Depends on the slot cost & availability : if Heathrow is at one end, you'd better go for big capacity
Depends on opposition : many small flights at different times will attract more people - if and only if there is a lot of opposition.