In the panIf you pan-fry, the very high heat of the pan will cause the bacon slices to "waffle", a bit like this:

And brown quite badly, rather on the ends of the slices, and not on the whole surface.
In the oven
The trick is to bake the bacon slices in the oven at 200°C (390°F), if possible on a wire rack placed on a baking sheet.

This way, they lose some of the fat that drips under the rack, brown evenly without warping, and become nice and crispy.
To sum up: to cook slices of bacon, it's better to cook them in the oven, rather than in a frying pan.