'85 London, RUN DMC, Whodini and some shouty white dudes that hardly anyone had heard of called the Beastie Boys. I was 12 and had my mind blown.
'89 London, Chilli Peppers touring Mother's Milk in a pretty tight venue (now gone) crazy moshing and crowd surfing. I'd been skating and listening to Uplift Mofo Party Plan. A lot.
See The Prodigy in '91 and '99. First was a little P.A at a Raindance rave second was a massive festival headliner. Both times amazing, I was pretty hammered both times.
If I had to pick one I don't think I could.