The "weight" and grade of "finish" will affect the look and feel of the printed page. Your preference amongst the options is not something we can advise you on. Check at a local printing shop, or paper specialty store, to get a hands-on assessment.
But if you are concerned with longevity (15 years, as you asked), don't worry. Most papers used in photocopiers and laser printing are low-acid and will last. (I have several printed booklets from the 1990's that are still looking sharp.)
That being said, if you are seeking to obtain a book that will truly out-last you, inquire about archival paper. If you take that route, I'd advise you not to be cheap on the binding and cover. Look for stitched signatures and cloth-covered heavy card. It will cost ($$$), but it will look hot.
EDIT: A 30lb paper (also labelled as "70# text") will have a nice weight, and will have very little show-through. Of your options for paper finish, just compare a regular piece of photocopier paper (unfinished), almost any college/university textbook (usually some grade of matte), and a magazine from a store (usually gloss or satin). What would you prefer?