Link work items or copy them?

If you're using TFS and work item tracking, you've probably seen that there is something called copy work item and something called link work item. But if you use these functions and take a closer look under the links tab, you can see that both results in a link to the original work item.

One of the differences is that copy work item copies fields which have the same name. So, if the original work item has a field called Feedback and the new work item have that field to, the value is copied. So, I've used Copy a lot of the time, to enable this nice thingy. The problem is that this causes other problems.

At my company, we use the excellent Scrum Dashboard from former Elektropost, now EPI-server. If you copy the work items, the calculations of work does not work properly. So, I'm back at using links again.