C.B.
I excusively expressed with both my kids.
I used an Ameda hospital grade pump that I rented from El Camino Hospital when I had my son last June. After two months of using it I bought a Medela Advanced...honestly, nothing beats a hospital grade pump. It definitely produced more milk than with the electric. If you are able - rent the hospital grade one to use at home, and use the Medela for trips. I'm not sure about the logistics if you work. Depends on if you have an office or somewhere private to take a hospital grade pump (it's actually pretty portable, and quieter).
El Camino Hospital has a lactation center that rents out quality medical grade pumps and pretty reasonable prices. I think I was able to do a weekly rate if you just wanted to try it out.