I know we are all built differently, but it's crazy to think that everyone can react different to different types of training. I've tried bodypart splits where I'm hammering each bodypart 1-2x per week with about 5-6 exercises for the main bodyparts and 2-3 for the smaller ones and I get little to no results. Meanwhile, if I go on an Upper/Lower where I'm hitting each bodypart 2x per week but with less volume and mostly compounds, I get great results. I just feel when I do the Upper/Lower splits that being done with my workout in 40-50 minutes makes me feel like I should have done more (mental thing). I've seen people grow like weeds on bodypart splits and people grow like weeds on 3x per week full body. It's just fun to think that there are different results for different folks.