When training 3 times a week, a full body routine will get you the best results. When training 4 times a week, I'd go for a upper/lower or push/pull split.
monday: lower body (quad dominant)
tuesday: upper body push
thursday: lower body (hip dominant)
friday: upper body pull
saturday & sunday: off
You shouldn't be afraid of overtraining, just make sure that you'll take an off day every other day when doing full body workouts or do some light cardio work on these days.