The interesting thing about citations in general is that they can help raise the trust of a company in the search engines, even without a link pointing to your website. Google sees mentions (aka ‘citations’) of your business name, address, and/or phone number (NAP) online as reinforcing the existence of the business. The web pages containing these mentions help to expand search engines’ knowledge of your business; thus adding trust.
Search engines can more confidently gather and interpret information about your business when there are more listings in existence that contain data about the business, and these listings contain proper data. For example IYP listings may contain your business’ hours of operation, description, category keywords, etc.
A specific example of this is how IYP venues categorize your company. In the case of a company that provides metal plating services, some IYPs may determine the category to be simply ‘metals’, which is a fairly generic topic, whereas another venue may put you under a very broad category of ‘manufacturing’ (which doesn’t even hint that you may work with metals). Other online business directories may contain slightly more specific category offerings such as ‘coating services’ where as others might hit the nail right on the head with possible ‘metal plating’ and/or ‘metal finishing’ categories.
In general, a company with more IYP listings and who’s listings are more correct and accurate, can have a better chance at ranking higher in search results as compared to a competitor when all other factors are equal, especially for local search terms (think ‘Milwaukee plating company’, etc.)
Just as search engines judge links from various websites differently; online business listing websites would also be rated as more authoritative or less authoritative based on Googles’ overall ranking processes. A plus to these IYP listings is that they also contain links pointing to your website. These backlinks would function the same way as links from a blog post or press release (in that they are all ‘votes of confidence’ of your website), however each may be factored into search engine ranking algorithms differently.
So, citations from larger, more popular, higher authority IYP venues would be technically more valuable than others, just as a backlink from a high authority website would be more valuable than a link from a brand new website with no backlink profile nor domain history/reputation.