It entirely depends, in situations like that don’t look at the backlink (although that is the ulterior motive), look at the following;
* Is the website in your niche? Does it offer visibility on your company/brand to people in your space that would benefit from clicking that link to your site?
* Does the website get significant, real traffic?
* Is the piece you’d be writing about, commenting on or ‘sponsoring’ going to add value to people who may be interested in your company?
If you answer Yes to 2/3 of the above, then ignore the backlink and whether it’s going to add value to your domain (it will, may be negligible depending on your niche/websites backlink portfolio, but it will in some shape or form) and focus on the PR alternative.