Stronglifts 5x5 is a beginner routine. It is on a similar level to the Rippetoes 3x5 routine. Madcow is an intermediate routine. There are other Stronglifts routines for intermediate and advanced lifters.
Generally, a beginner routine is better for a beginner because a beginner routine has the trainee making progress on a workout-to-workout basis. An intermediate routine has the trainee making progress on a week-to-week basis.
By extension, if you are still at a point where you can make workout-to-workout progress, whether because you are a true beginner (0-9 months working out generally) or because you are returning from an off period, then it's better to choose a beginner routine. If you can no longer do that, then you are an intermediate and it's time to plan for weekly progress instead of workout-to-workout progress.
By contrast, if you are an intermediate trying to do a beginner workout, you are going to plateau very quickly. And if you are a beginner trying to do a intermediate workout, then you are wasting time by progressing much slower than you are actually able.