Hitter every time. It is tough to ever consider a pitcher as a #1 prospect.
Just look at the pitchers who have been Baseball America's #1 prospect since 1990:
Daisuke Matsuzaka, Josh Beckett, Rick Ankiel, Brien Taylor, Todd Van Poppel and Steve Avery.
The hitters who have been BA #1 prospects since 2010:
Jackson Holliday, Gunnar Henderson, Adley Rutschman, Wander Franco, Vlad Guerrero, Jr., Ronald Acuna, Andrew Benintendi, Corey Seager, Kris Bryant, Byron Buxton, Jurickson Profar, Bryce Harper (2x) and Jason Heyward.
Profar and Benintendi are the only players on that list who aren't bonafide stars (besides Holliday and Franco due to extenuating circumstances). Generational pitching talents flame out regularly. Best case scenario they win you a World Series first like Strasburg, but often times they don't.