I wouldn't know how to decide between G4's performances, there were so many that were so different but equally good.
Agree with what others have said about You'll Never Walk Alone. There was something else that came across with this performance, you could tell it meant something.
Circle of Life, fabulously done, one of my favourites. Just left me with a big smile on my face, no way they deserved to be in the bottom two with that. They sang their socks off and it was just brilliant. A real comeback after Britney.
Bohemian Rhapsody - they managed to chop up and condense a 7 minute song and it worked. Real drama, great entertainment, vocally spot on, great the way they vocalised the instrumental. Loved it
Somebody To Love - Did something to me, this did

loved the choreography, didn't find it camp at all. Jon vocally not right, but didn't detract from a thoroughly professional and charismatic performance.
Can't not mention Nessun Dorma. Arrangement was great, they needed to keep it simple. A huge aria for one so young, and Jon nailed it. Respect
If I had to pick one overall, it would have been Creep in Dublin. Not technically a performance, but it was the real defining moment of the series for me. They captured something that day. Magic.
A bit of a cop-out I know, to mention so many, and believe me, it's unusual for someone as critical as me to be so torn. They just kept pulling stunning performances out of the bag. I hope they have a big future, they certainly deserve it.