I am afraid what really matters to an engineer is always about the availability of the product and its support/tools to ease the design (programming/updating in case of MCU).
For example, the first MCU, I was able to get its IC and its complete datasheet, was AT89C2051... So my preferred series is now C51 ATMEL MCUs (and its equivalent as the flash MCU, SST89E58RDA, which has the In-Application Programming feature).
So if any of the students will be able to work with real PICs while using his own PC to build a few interesting projects, I would be surprised if he will look for any other series.
Kerim