16u is prime college exposure in Ohio and surrounding states. If you team is heading out to the "big time" on the west coast, I believe 16u and 18u are both heavily recruited. But it is a different animal in this section of the country.
Kids in Ohio almost always earn DI athletic scholarships at 16u, especially pitchers. Stock drops significantly after the 2nd year 16u season, so it's VERY important to prepare WELL BEFORE that season comes. Her team MUST attend heavily recruited competitive tournaments, and she MUST have contacted college coaches by her 16u season to let them know of her summer schedule - and STAY in contact with them.
At Stingrays this past summer, most of the kids on the top 18u teams were already "spoken for". The 16u teams were drawing the vast majority of attention.
NCAA DII, DIII and NAIA may be weighted differently in terms of what age group they recruit, I am not too familiar with how they operate.