Staggered poles were introduced to match the heavy radius of the finger boards which made some of the strings further away from the poles than others, which resulted in some strings being quieter than others (To Leo fenders ears anyway) Previous to 1954 the poles on Teles and the original P-bass were flat, then in 1954 the first stagger was introduced to strats, then changed again in 1956.
If you have a flat board its best to stick to flat profile, if your fingerboard has quite a heavy radius, a stagger would be the best option.