Here’s a great big table that compares all the thesis reference tools that I have played with. Hopefully it will help you to choose which one suits you best.
|Price||Free||Free/$250||$79||Free/$55 per year||$100 per year||Free||Free|
|Citation plugin for Word|
|Search databases for new papers|
|Access your university library system to automatically download papers|
|Text search your own papers|
|Recommendations based on your papers|
|Share references in a private group|
|Social network component|
It is safe to assume that I have messed something up in this table, please post corrections in the comments and I will get it sorted.