There is no single answer to this, which is a common occurrence with SEO. You see search engines are not merely made up of a single algorithm which we can set our sites on to figure out. Quite the contrary; think of it as layers of an onion.

There is a core mechanism to which other methods and approaches are added. Each time a search engineer adds another layer it becomes exponentially more difficult to sort out. Then consider that each layer in that onion has a set of parameters that can be adjusted to create a slightly different outcome (search results). Much to the chagrin of your local SEO, none of us know exactly how it works.
Now, that being said, we do understand some aspects relating to inbound links and how they are (potentially) treated. Each website or more specifically, each page; has what we like to refer to as a link profile. This simply means the totality of the back-links and the potential value each may hold. Simply having more back links than a competitor is not the end-game here. Quality is often more important than quantity.
The basic types of links are;
1.    Reciprocal Links – links pointing to your site and you link back to them.
2.    One way links – links pointing to your site without reciprocation.
Now, each search engine will have their own feelings as to what is valued and how. A basic page segmentation approach give us the following in order of value (mine not a given engine);
1.    Editorial; links that are in the actual content of the page.
2.    Side Panel; a link from the side panel of a given web page.
3.    Header; a link to your site from the header section of a web page
4.    Footer; a link that comes from the bottom navigation of a page
5.    Site-wide; links that are predominant throughout the site (a forum sig for example)

Now we can add on factors that affect a given link. Each link has a weighted value depending on the search engine and how they deal with link valuations. As a general rule some of the following come into play;
1.    Age of the link (how long it has been around)
2.    Topic and/or Title of the page the link is on
3.    Relevance of the content of the page
4.    Freshness of the page (has the page it is on been updated)
5.    Number of links on the page (some ranking systems pass a ratio of accrued value)
6.    Trust (is the link from a trusted page or a suspect domain)
Link Profiles – to expand the concepts a search engine also looks at the entire portfolio of incoming links to create what we call a ‘Link Profile’ – with this larger global view of your backlinks they can valuate it and even apply temporal metrics such as;
1.    when links appear or disappear,
2.    the rate at which links appear or disappear over time,
3.    how many links appear or disappear during a given time period,
4.    whether there is trend toward appearance of new links versus disappearance of existing links to the document, etc.
By doing this they can assess trends and potential attempts to game the search engine by artificially inflating one’s profile. Temporal factors are also important in assessing the current popularity of a site on a chronological scale.
And so which is best? I would say a topical/relevant, one-way link that is in the content (editorial) from an Authority site in you nice (market segment) – those are the best. In the end it is more about creating a logical and balanced link profile.