In my analysis, it seems that there are several features that Knowledge Base (KB) has that would make it edge out the free Solutions framework, and the rumor that Solutions is no longer being developed certainly means something significant.
However, aside form the cost, there also seems to be a lack of customization in the KB framework that makes it worthless for anything aside from its expected out-of-the-box use.
What are the differences and advantages of each?
First to start with: The only benefit of Solution over Knowledge Base is: Solution is free!!
Now how knowledge beat solution big time or can say why salesforce is making more money by introducing this:
Unlike Solutions, using the knowledge base requires Knowledge feature licenses, which come at an additional cost.
Unlike Solutions, Knowledge comes with a suite of reporting and analytics to give you insight into your knowledge base, article statistics, and ratings.
Although Solutions continues to be supported, Knowledge is at the forefront of Salesforce iteration and development. Expect to see continuous improvement and enhancements in Salesforce Knowledge.
Knowledge allows for article segmentation and categorization with data categories. With Solutions, you can’t expose different Knowledge articles to your internal team than you do to your customers.
Knowledge search and integration with cases is more advanced and leads to quicker case resolution.
Unlike Solutions, Knowledge leverages the Chatter feed and a publishing approval process for enhanced team collaboration.
Knowledge Articles support rich text format like a Word document, while Solutions don’t. That means no bolding or italicizing; just paragraph breaks between plain texts.
Long story short- Solution is Prius what runs just fine with is limited features where Knowledge is Shiny Mercedes with Intelligence to calculate on it's own based on your records with some other cool features but it is expensive.
solutions, so I won't make this an answer. I know from experience of investigating both and KB was the winner - mainly for the reason support forsolutionsis discontinued. Some features may not be attractive depending on your situation - i.e. segmenting articles for internal, external (portal users), and public; fairly flexible approval/deployment process; searching/filtering by article category; compatible with Service Cloud. Good luck!