I was going to say Hammersmith. I've heard the very very worst sound at that venue (Ocean colour scene), but have also heard some good sounds. At Brixton, I've heard some absolutely awful sounds (Pogues the first time I saw them, although they sounded great the following year, Placebo, although that is probably because they're shit). Thought the Pixies sound was pretty good though to be fair. My main gripe with Brixton is simply that they seem to be selling more standing tickets than ever, and it doesn't actually feel entirely safe, let alone comfortable. Only a few years ago, you could go to a sold out gig, and move quite easily through the crowd. Big respect to the fact they allow you out to smoke though! That is an amazing plus point, as I've been gagging for a smoke at the last few gigs I've been to!