ServicePrograms VS normal Programs

Hello everybody!

I read some articles abouth service programs and now I am wondering is it 
better to make a service program with collection of subprocedures that 
will be repeatedly called (with callP) from other programs, or is it 
better to have every subprocedure as one rpg program (and call it with 
call). What is diference in performance? What is exactly happening when an 
program calls subprocedure from service program with callP and what is 
happening when program calls another program with call and parametar list.

I am asking this because I am Java programer and fresh RPG programer and 
most of RPG things I learned from IBM's student books and Sourcers Guide, 
but my collegues (who code in RPG all their life) have totaly diferent 
aproach that doesn't meet any ruels (described in RedBook) of advanced and 
modern coding.

Thanks, Igor.