What are the differences in the VisualStudio Add-ins for Mercurial?

I'm evaluating Visual Studio Add-ins for Mercurial. Currently, I've identified 3 potential candidates :

• VisualHg http://visualhg.codeplex.com
• Mercurial Toolbar : http://mercurialtoolbar.codeplex.com
• HgSccPackage : http://www.newsupaplex.pp.ru/hgscc_news_eng.html

I'm looking for a comparison of features or capabilities.

Features that are important to me are: a tool that integrate well with VS, Open Source, actively developed, and robust.

Well, let's compare the details of development:

• VisualHg's page says it's stable. The last version release was March of this year and the latest changesets in the source are from 1 week ago.
• HgSccPackage (better found here than your other link) was last updated in the VS Gallery 2 days ago. (It can also be found on bitbucket.)
• Mercurial Toolbar's page says it's in alpha and was last updated March 2010. Of the three, it appears this one is not actively developed.

It appears [from skimming some text] that HgSccPackage has its own windows for graph logs and whatnot.

VisualHg on the other hand is more of a supplement to TortoiseHg. Many of the menu commands for VisualHg will open TortoiseHg windows. If you use TortoiseHg's UI, this consistency may be preferrable. From the screenshot I saw for HgSccPackage, you may find VisualHg's status icons more standard, as well.

Since you have only 2 choices, it really doesn't take much to try both and see which you prefer.

I have VisualHg installed, but tend to use TortoiseHg's Workbench more than VisualHg. VisualHg stays in use mainly for its automatic add, remove, rename, etc.