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

I have just finished researching the same question. It seems that VisualHG had its last version released a year and a half ago in Oct 2011. In all 2012 it had just 3 commits. Last version of HgSccPackage was released in Mar 2012 which is roughly a year ago, but it had a bunch of commits since then.

It seems that both tools are equally powerful, but HgSccPackage recieves more investment. I decided to go with HgSccPackage.

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.