Best - Sonata Arctica. This was before Jani was kicked out of the band and before they made that abomination called Unia. The energy was great (except for the bassist who just stood there with a blank stare the entire time in the back of the stage), the singer's pitch was ridiculous, and it was the best live tone I've heard in person at a concert hall. It was a smaller venue, so the energy was awesome.
Worst - Hard to say. I know it's not metal, but when I went to the G3 concert, Petrucci was so loud that I got dizzy. He fucked up my hearing so much that I couldn't hear Satch or the jam afterwards. I couldn't even tell what he was playing because it was so loud. Everything sounded like white noise. My hearing was shot for a few weeks after that. On the other hand, I went to the first Gigantour, and everyone decided to have a stupid loudness war. After every band, everything got louder and louder. In case you don't see a pattern here, I'm not a fan of really loud concerts. When you have to grimace or hold your ears just to stay in the hall, it doesn't become enjoyable.