I think it is mostly personal preference and finances. I have been using 2 used Medela pumps. One was quite old and one new. Even EP'ing, they both have been wonderful. No issues with either. The pump I gave away was a Medela Traveller, which is from 2004, and that thing is amazing. I actually miss it, lol.
You will need to get new breast shields, valves and membranes, and collection bottles. This kit is everything:
Amazon.com: Medela Breast Pump Accessory Set: Baby. For conveinence sake, if you will be pumping a lot, get tons of those collection bottles. I hear the Gerber ones fit and are not as expensive as the Medela ones. I have 12 of them. I store the milk in the fridge in these containers so I need a lot.
What I did was put a wanted ad on Craigs List. I said I wanted a new-ish PIS Advanced version (be sure to get this version, and not a really antique one, lol) that had not had a lot of use, and I was willing to pay $85 cash. That's a really low price so I didn't expect anyone to respond. But I did get a barely used one for that price, and I am thrilled with it.