16GB vs 32GB Speed - Samsung Galaxy Tab S 10.5
The difference is so slight though that the difference will be unnoticeable, but the larger hard drive will be faster.

As requested:

http://www.tomshardware.com/reviews/understanding-hard-drive-performance,1557-10.html

In addition to the statement at the top in several diagrams you can see that hard drives with the same specs but different sizes have faster read and write times as the size goes up for a majority of the tests.