Totally agree when you said Rescue Diver is the most challenging. It's very physically demanding with all the dragging and carrying people around. (I had to carry two Brits who were a foot taller than me!) Those were the days I'd eat a full plate for dinner and then just crash into bed because it's just so exhausting.

Diving is plain good stuff. Regardless of which training agency, it all boils down to the diver on how they apply the theory and observe proper diving etiquette ***although I'm PADI all the way haha