https://wiki.mobileread.com/wiki/E-book_Reader_Matrix
Hi Gilda, welcome to Mobileread
The two ebook readers that you are considering are from very different approaches. The Kindle uses the eink technology while jetbook is a backlit screen.
The advantages of eink devices are the longer battery life between charges (several weeks vs less than 1 day) and the more paper like appearance. The backlit screen does allow you to read in the dark without a supplimental reading light.
I would definitely suggest that an eink device be top on your list. Then the question becomes "where will you get your ebooks". If you will purchase most of them, then Amazon currently has the most attractive price and the largest selection. But Kindle currently only reads Amazon's proprietary format mobipocket and pdf. If you want to get your ebooks from multiple places, or download them from a library, then your should probably look at the Sony products or the Astak pocket pro. They both read drm'd epub and pdf books. I've included a link at the top to a wiki that compares eink devices.
cheers