As now google is giving more preference to content so article submission is a good way to create backlinks and it also helps in getting higher rank on search engine pages. Whereas forum links give you good traffic to your site but it may be relevant or may not be.
Both are important but article submission have a upper hand when it comes to quality back links, but again for article submission you need quality and unique content every time.
Forums link is far better than article links but the matter is forums link from your related theme website. Because as compared to article links, forum link is an easy and better way to get more traffic on your traffic on your domain site.
Both have their own importance and advantages but Google likes CONTENT a lot so I will say Article Submission is a better option. You can try both for this purpose.
In my opinion, both article links and forum links have own importance in the process of SEO, were article links are important & helpful for ranking & forum links are important for generating the traffic.
I think they both have their own positive:
- Articles focus on quality contents and will help you receive "truth" from google
- Forums focus on link's number and will help you improve contact quality and your site's popularity
Well, the update of Google shows that it is quite familiarize with the content except anything. So, an article will help more than what you do in forum. An interesting and informative article has the power to block the readers on it which can help your website to generate customers for it easily.
Always try to go for both because getting links to your website from a wide range of high-PR domains is great for link building. However, if you have to choose one over the other, then go with article content because Google gives preference to fresh, high quality content. Although writing articles takes more time compared to writing forum posts.