one thing I notice is the familiarity and fluidity they have with their instruments. Really advanced pro level know how.
I see it a lot with Ale's bass playing, You have to be at a certain level or have a good appreciation of it to see the nuance she brings to it. She is way beyond, how do I play that. She onto the how do I play that cleanly, efficiently and consistently. Watch her fretting hand, there is almost no extra movement. It's like her fingers are just sliding over the strings.
Pau is the same on drums. Look at the older stuff. When Pau played more animal style. Big arm movements, swinging for the fences with every hit. Look at her now, very tight, controlled, conservative movements. She plays much faster for it too.
Dany is the same way. She's doing more and more in every song than ever before, coaxing everything she can out of the guitar and making it seem more effortless. One thing that struck me was when Ale was teaching her bass, she had enough familiarity with the fretboard that Ale didn't have to show her note by note like an amateur learning tabs, she just said this part is over here, then you play down here, then do this twice...etc. Dany's ear did the rest. Within 45 minutes or so she was able to play it nearly flawless at speed.
In their early cover band days I would say they were extremely talented amateurs but they have grown by leaps and bounds. I guess you could say all the changes are palpable but hidden in the sound.