I'll give a BLS (PB) perspective. I work on a truck that has changed pumps over the past few years... It's my understanding that there are many many pump options, and almost everything used in a hospital could be used in a truck, but there are a few criteria that make some models easier to use than others-- depending on your service and call types...
-- Size-- clearly the model you use must be reasonably portable, and fit not only in your truck (with a place to be plugged in), but also on your stretcher (on the IV pole or elsewhere without interfering with other equipment).
--Battery-- ensure the pump has the internal battery capable of working for the length of your calls. There will be times when you're too busy, or it's too complicated to plug it in in the truck (while service the patient), so can it last for the entirety of the call, and be ready for your next? Are the batteries capable of "smart charging" if left plugged in at all times? Are the batteries hot swappable?
-- Cost and compatibility of drip sets? How much are requisite drip sets? Are they compatible with hospital sets? Are both "full sets"-- connecting an IV bag to patient and "half sets" extending existing tubing available? If you're doing IFT, what's easiest for your care?
-- Medical Director approval-- What does your supervising MD have to say about this? DO they want a system with medication names and dosages pre-entered to reduce errors? Do you need medical control approval for certain medications?
-- How many channels do you need? How many different infusions will you need to provide at a given time?
--Setup time- How long does it take to set up a medication infusion? Is that practical when you need a dopamine or nitro drip? How about continuing an existing drip for transport? Is it practical for you to have different equipment for emergencies than for transfers?
-- PMI/Maintenance-- Are you able (or willing) do it in in-house? How practical or expensive is contracting with a company to inspect and maintain your pumps? How much downtime is expected? How many extra pumps do you need to maintain as backups?
Below are some of the "popular" pumps at services in my area...
http://www.buyemp.com/product/alaris-medsystem-iii
OR
http://www.carefusion.com/medical-products/infusion/alaris-system/medsystem-iii-infusion-pump.aspx
http://www.buyemp.com/product/abbott-plum-xl-i-v-pump
http://www.zoll.com/medical-products/fluid-resuscitation/power-infuser-pump/
Good Luck!