Teams are usually smaller (couple of dozen people, although I have seen teams, like Team Air Force or Team Skunk, that are much larger) lower-key operations made up of an already existing group that gets together for RAGBRAI; this may also carry over to other rides and events. May or may not own/operate a team vehicle of their own. The first teams were a bunch of people who probably kicked the idea around over a couple of beers — “Hey, wanna do RAGBRAI? I know where I can get a van to carry our stuff; we’ll split the cost for gas and take turns driving (or my GF will drive it) and the rest of us will ride” — and it quickly escalated to party buses, Ryder trucks, trailers, circus tents, and segregated camping areas. Many existing cycling clubs also form teams; and some teams have evolved into clubs of their own.
Charters, like PBV, Bubba’s, and Bikes to You, are generally for-profit entities that run the gamut from providing minimal services (a ride to the start/from the finish to a central point and gear shuttle during the week) to a fully supported, fully staffed, “mint-on-the-pillow” type service where just about anything your little heart desires is already included or can be arranged. Shelter, food, repairs, showers, refreshments, etc. are all provided for; in fact, I wouldn’t be surprised if one of these coming years some charter will provide a bike for you as well and all you need to do is show up and ride. Will sometimes refer to themselves as “outfitters” in the same vein as those companies that will set up and handle all the details for an Everest expedition, a big-game hunt, or a rafting trip down the Colorado River.
I’ll leave others to outline the various pros and cons. I’m afraid my personal biases would become too apparent.