Sizing varies across different types of bikes, between road bikes and mountain bikes, men’s and women’s models, and individual manufacturers.
If you are looking to ride more aggressively on uneven paths with steep slopes, you might want to consider a bike with a small frame size so that it can maneuver easily.
Alternatively, if you are looking to ride faster on flatter paths, you would want to choose a bike with a bigger frame size.
Ultimately, it will depend on your comfort level and your riding style.