It depends on what you want to teach.
If your intent is to teach object oriented programming then an OOPic is the logical choice.
The UBW can read/write, do ADC etc under the controll of a PC over the USB connection. No programming required, the control code is all on the PC.
When and if students are ready they can modify the UBW code or replace it with their own. If you replace the UBW code it is becomes a bootloadable 18F USB enabled target/controller.
It gives you the best of both worlds. (PC and local control)
It is also inexpensive to buy or build.
I suggest you buy or build one and give it a try.