Both tablets are intended for use with a digital pen. In contrast to previous versions of the entry-level iPad, the new iPad will work with the Apple Pencil. The Galaxy Tab Active2, meanwhile, works with Samsung's S Pen. The big difference here is that Samsung packages the S Pen in the box with the Tab Active2, while the Apple Pencil is sold separately from the iPad (for $99). The S Pen is also housed within the Tab Active2 itself (or, to be precise, the pen is housed in the rugged case that's included for the Tab Active2). The Apple Pencil has no such storage option within the iPad.
Lastly, Samsung notes that the S Pen is water resistant (it features an IP68 rating), meaning that users should be able to use the pen "even in the pouring rain," according to the company. Apple makes no such promises of water resistance with the Apple Pencil.