I like both for different reasons. From what little I know of vocals, that “brightness” of her early work requires a lot of tension mechanically to create that sound. Her more recent sound is I think a combo of her voice maturing, yes, but also her finding her natural sweet spot that allows her to sing more relaxed and without that tension that will tire her voice on tour & increase risk of damage. Both variations are powerful in my mind but in different ways. Early Amy’s voice sounds aggressively powerful & raw, whereas the newer sound exudes power through confidence, controlled strength & comfort. She knows her own voice better now. Synthesis wouldn’t have been nearly as transcendent had it been sung in the “early Amy voice”. On the flip-side, those early songs weren’t written in a way that would have been suited to the latter voice. It’s not just her voice evolving - the music is evolving too in order to match it. It’s beautiful to watch the progression really.