An Adobe Digital Editions ebook is almost always a PDF (and it certainly a PDF if there is also an Adobe ePub version).
I don't think there is any reason to go with MOBI over ePub.
On your slate, the PDF might be the best choice for a heavily illustrated ebook (or for a technical ebook with page layout designed to aid comprehension) but in general an ePub will be your best choice for reading on a wider range of devices. However, I'm not sure how well ePub works on the JetBook.
For more on various formats, see
A Comparison of format limitations based on The Hobbit.
Note that on a PC, Adobe Digital Editions is a relatively poor PDF viewer. If you strip the DRM then you can instead use Adobe Reader or Foxit or whatever you like best. Adobe Digital Editions is better at ePubs, but you can instead try Sony eBook Library or B&N Reader. If you strip the DRM, then Calibre or FBReader are also possibilities for ePubs. FBReader on the PC should be similar to the JetBook for ePubs, although the PC version of FBReader is significantly newer than on the jetBook.