Many people will recommend to do the opposite of whatever your league is doing. So, if the league overall leans strongly towards college, go the other way, hoping to get a future ML player in Round 2. Trouble is, with 31 other teams, most leagues are pretty close to evenly split HS/College. If yours isn't even, take advantage of it.
Personally, I go towards HS, because those players are more tradeable. People will be skeptical of a 25 yr-old prospect already having 3 years of development. The same 21 yr-old looks like he has higher upside.