At whatever level, the inside-outside call is touchy. Umps set up in the slot over the catcher's shoulder (inside) and only see "perfectly" on that side. The outside ball is harder to call. High and low changes from batter to batter, depending on stance, and the high side is - I think the rules still say - armpit to top of knees. These days, anything much hogher than belt is not going to get you a strike, but a lot of umps will call a strike at mid-knee or even a little below. And don't forget, it's where the ball is when it crosses the plate, not necessarily when it passes the batter, who may be at the front or back of the box and close to the plate or back from it.
Knowing the particular ump's tendencies, and figuring out as you go, what he's gonna call is part of the game.
Again - the best thing is to have consistency. I don't care if he gives an extra bit outside or low or whatever, as long as he does it every time.