depends, but not really. Something like plumbing.biz would probably be better than plumbing.mobi...but something like iphone would be better in .mobi than .biz I would think. Also, dot biz is really only worth it if its a common one worder if you ask me. Honestly, I don't think .biz is worth a darn and wouldn't waste my money on it.
if you like to set up a business site, .biz is better, you like to have mobile site, .mobi is better.
I personally think the value of any top level domain Extension depends on how it is found on the Internet. First most of the world thinks (dot Com) when they think Internet. So .net, .org, .biz, .us or any other extension except .com are initially of equal value. SEO (Search Engine Optimization) levels the field and makes all domain extension values equal including .com. The keywords included in any domain name are far more important than the extension. And like conveying any information, use the fewest words that say the most. Just my opinion, thanks, Moe Cobb