The core basic principles that apply are the following:
- Total volume per body part is the biggest driver for muscular hypertophy (growth)
- Manage recovery to enable adding volume over time
- Work you enjoy ensures you are going to keep doing it
Beyond this, studies have shown that there really doesn't make a tremendous difference the shape of the volume (sets * reps) or the order in which you work the muscles.
You have several ways of breaking down your work, which can be by muscle group or by movement. I personally am a fan of full body training 3x a week, but selecting different sets of isolation work. As an example, I will have a push, pull, and squat variant every training day, alternate between biceps/triceps and shoulders for isolation work, and then whatever else I need. However, that's just how I like to do things.
To boil it down:
It just doesn't matter. Just train the way that feels most natural to you, and incorporate new things over time as you focus on "problem areas".
Keep in mind that compound movements that use larger muscles do trigger more growth than isolation movements alone. However, if you add in isolation movements after compound movements, you'll see increased response in those muscles.
While I do a full body training day every time I work out I manage fatigue by having different training styles. Example:
- Heavy day: 85-90% of my max, 4 sets of 2-3 reps
- Rep day: 75-80% of my max, 3-4 sets of 8-12 reps
- Speed day: 65-70% of my max, several sets of 2-4 reps
The heavy day helps get the body used to heavier weights to enable increasing weight over time. The rep day is the meat and potatoes of getting stronger. Speed day is kind of a mental break and active recovery day--while focusing on moving weight quickly. Since I have 3 main compound movements, I alternate which one gets which emphasis. I also make sure each main compound movement gets a different emphasis for that day. That way I'm not going heavy on bench and deadlift in the same session.