...is not the only number you need.
While the trip fuel might be quite similar and cycles would be identical, flight time on the 737 ought to be substantially less. There is one saving.
Now why on earth would you be running numbers on an almost-empty 737? The RJ
carries 85 peeps. 737-300 should carry 8F and 128Y or, single class, as many as 140 or so. If it is dollars you are concerned with there
is the significant number.
Then there is maintenance and dispatch reliability. We can talk all the THEORY
we want here but here is an indisputable fact for you.
Twenty years ago there were BAe-146 and B-737 operating the very routes you ask about. Three airlines had the BAe, Royal, PSA and AirCal. Today there are none. But there still are 737s flying these routes.
Overall economics. Not just fuel burn, even in this day of higher fuel prices.
Happiness is not seeing another trite Ste. Maarten photo all week long.