I've been using TortoiseGit for a while. Whilst it's true that git's performance suffers on windows, it's going to be perfectly acceptable in most situations. Of the three that you mentioned, Git certainly has the most polished "Tortoise", in my opinion. And if you're used to using TortoiseSVN, the transition to Git should be pretty smooth, as TortoiseGit is based upon the TortoiseSVN code base and reuses a lot of it's UI and design principles.