I am going through something similar, trying to choose which piece of equipment to purchase that will work for almost everything in my high school math classroom. I will be teaching AP Stats in our building next year so need a fully functional office excel, photos, video, internet and also have the downloadable apps option. I also need something that will run external programs. After talking to others, the newer Microsoft Surface Pro is the direction I am headed. It has the functionality of an iPad and also a laptop but in the size of a tablet and has a USB port.
It is a very nice machine, as an all in one, although a bit more pricey. But I will save money by not having to purchase software we already have for desktops and the camera option is included as well as office.
Good Luck figuring this out!!