Well it's a bit of an unfair comparison as BBCi is intended to be a worldwide source of news and information, whereas BBC World clearly isn't. It's like comparing the British Government to Horsham District Council.
Don't forget that BBC World also publicises bbcnews.com for people wanting news.
Yes, BBC World.com is just a service to find out the channel listings and details of some feature programmes, or a bit of background information about BBC World.