The tradeoff is really ease of administration and integration with your corporate security vs. the need for every user to have an Active Directory user account. AD accounts equals licenses, so cost might be a consideration.
If you are a corporate user and tha majority of your users will already have AD accounts, then this might be the best choice for you. You can implement role-based permissions using AD security groups, rather than managing individual users within VisualSVN. If you have a lot of users, this can greatly ease your admin burden.
On the other hand, if you don't want to pay for Client Access Licenses, if a significant proportion of your developers are outside your organisation, if you;re a hobbyist of if your development team is relatively small, then the lightweight Subversion authentication fits hand-in-glove.
I have chosen the SVN authentication, even though I already have all the Active Directory infrastructure, because my development group is a collaborative voluntary venture and the SVN authentication is really easy to set up and use. The only down side I've found is that the users can't set their own passwords. It is a shame that SVN doesn;t support both in parallel - like SQL Server does.