As far as I know electrocompetence is more efficient (I guess you want to introduce Plasmids?) but also more costly. The cells usually return rapidly to their original state and the competence is only temporary.
I am preparing electrocompetent E. coli myself, the procedure is simple, but requires one day and several centrifugations. The resulting cells give usually 10exp9 colonies per microgram of supercoiled plasmid. The cost is low, you need only broth to grow the cells and sterile water to wash them. With chemicompetent cells, the efficiency is usually 100 times lower.