Assuming you get a 'dofollow' link ? If you are in it for the long run, get a link in an article. If you want pagerank, go for the homepage blogroll. Sitewide links work if you are the only sitewide link off the domain and even then a blog-roll link would probably work better.
So a blogpost or artcle with a dofollow link is best? Im not bothered about my pagerank just high SERPs!
Well, links from blog pages that are closely relevant to your website can be of high quality and helping with your site's rankings. The homepage links too can be helpful, especially the ones which are coming at the higher spots of the pages because the footer links might not be that important.
sitewide links are devalued these days and dont worth the same as they used to be in the past. homepage links are fine but blog posts or other presale pages/social media/web 2.0 pages can offer highly relevant and quality links. you can read my recent blog post for more info