I have three pumps:
cheap walmart electric - gets used on every inflatable I own
4 inch carlson - for topping off big boat
k pump - for topping off little boat and cataraft
Ideally, everyone should have at least two pumps...one for volume and one for pressure.
I always start out with my communist electric, which happens to be an ass kicker. My K100 is a great pump and gets used a lot more than my Carlson. It is also easier to stow and goes down the river with me on every trip. However, for my big boat I use the Carlson because just topping off that pig is a chore. As someone mentioned, if you are on a multiday trip, the Carlson is where it's at.
I have inflated my big boat using just my Carlson(no electric) and it is a workout. But, if you only buy one pump, get a Carlson. Or better yet, if you have friends who know how, have them help you build your own pump. My brother once dismantled a Carlson, studied it, and built his own and it works great.
For a big 16 ft raft, you should at least have some kind of electric pump from walmart, amazon, etc. They are very inexpensive and work great. But if you only bought one pump, the 6 inch Carlson is the best I have used.