SDL TMS or Idiom WorldServer?

Question from one of the subscribers to this blog:

"We are in the process of bringing on a workflow tool. In general, for software, DITA/XML, and Frame files, do you prefer working with the SDL Translation Management System, or Idiom WorldServer, or another program? I have my own ideas, but I'm always curious to hear the opinions of other localization professionals."

I recommended asking pointed questions to ensure the chosen vendor/solution:

• doesn't lock you in to a particular LSP, or out of freelance translators who won't have the tool
• manages the native file formats, without conversion
• allows you to talk to internal technical leads (not just salespeople)
• offers integration with your version control system, so that you're not manually moving files to and from your engineering repository.

Those of you with experience using these tools, kindly comment.