Brought in via a waiver claim this offseason, Sam Hilliard is very similar to Ryan McKenna as a player. He's a defense-first outfielder who can play all three spots when needed but is limited with the bat as evidenced by a .215/.294/.424 slash line.
With both Hilliard and McKenna in the picture entering the spring, the Orioles will likely end up choosing one of them to be the fourth outfielder and primary defensive replacement, with one of either Cowser or Kjerstad being a fifth outfielder thanks to the crowded outfield picture right now.
Just because the Orioles will likely pick one of them doesn't mean they should. Let both kids play and try to sneak both Hilliard and McKenna through waivers. If either Cowser or Kjerstad falters, then the Orioles can re-evaluate things.