The Art scene is much bigger in London, perhaps with the exception of street art here. Things like first Thursdays is great. Hackney wick has a fantastic community of artists and designers, not sure BA has an equivalent. Plus the wealth of independent art galleries not to mention the amount of independent creative studios. Top that off with the ones we know about like the Tate Modern, Tate Britain, Portrait gallery...As a Londoner I find your statement confusing. What does BA lack? Arts scene? Music scene? Personally I think it is much more lively here. And, other than a few dreadful clubs, London closes at about 11.00pm, which is when (even at the age of 46) I am just warming up.
Are you really from London, England???
Music scene is fantastic in London. Any night of the week you can go out and see a lot of different types of music from hipster type stuff in Dalston / Shoreditch / Hackney, to massive stuff at the O2, Wembly, Brixton. Not sure how BA can rival this.
Ok things do close in London early but then we go out earlier and I'd rather take that than waiting until 1am to see a band. There is a dead time here between end of work, 6pm and 12 midnight, thats 6 hours! There are a couple of clubs here like Niceto vega that are decent.
The 11pm is a thing of the past as a lot (not all) of pubs are open until 1am now.
Perhaps your just out of touch with modern London...