Sharp and fast or slower with big break?

Ok I am refering to the last 3 games I have pitched in.
The first 2 games I was throwing my splitter pretty hard and it had sharp downward break starting belt high and going to the shins and sometimes lower. The resuly I got in these games was alot of outfield hits which seemed odd to me. Even though they had to swing so akwardly at the pitch they were hitting its pretty solid. They would dip their entires body and kind of guide their bats at the ball. the third game I was throwing to slower with bigger loopy break and they werent hitting it.
Should I keep the sharper faster break or go for the looping slower break? Or should I just see whats happending on any given day and adjust for that?

I would use both, personally.

adjusting to the pitcher is part of the game and they adjusted to your sharp splitter because the break was less and they knew when it was coming. the slower had a bigger break which is hard to hit until you get in a league were hitters have more talent. you should use both