I have never flown into Barcelona and am wondering how long it usually takes to get off the plane and through customs, etc.? We are used to long lines at CDG and allow several hours but perhaps Barcelona is more organized.
My educated guess is that Barcelona takes shorter time not because is more organized but because it has a much smaller airport than CDG.
I flew into Barcelona airport once recently and don't remember much delay, as it is relatively smaller and easier to navigate. Are you asking this question because you want to buy a non-refundable train ticket for the same day? If so, allow plenty of time for flight delays. If you're staying in Barcelona, then the key is usually just to arrive while the Aerobuses are running (until about 1:00 a.m.)
Customs only applies to flights from outside the EU, and passport control only applies to flights from outside the Schengen area, and passengers from other EU countries go through the fast lane.
If you are a US citizen coming flying outside Europe, the questions is really, how many flights from outside the EU/Schengen area does Barcelona get a day? ANSWER: a lot less than Paris Charles de Gaulle.