In VS2015 it's possible to "ignore white space" when comparing clicking a little icon with the =
symbol.
Go to "View/Toolbars/Compare Files". In the toolbar click on "Ignore trim whitespace".
Update 2020: we struggled a lot solving conflicts with VS comparison tool and the Tortoise SVN one, so after a research we decided to install Devart Code Compare (free version) which has integration with VS2015/2017/2019, SVN (Tortoise and Ankh), TFS, Mercurial, GIT, etc. and Windows Explorer, so no more nightmares/confusion between different comparisons tools. Give it a try, it's extremely useful. It has also Merge to solve conflicts and Folder diff, which is really useful when SVN does not merge for some reason. Also, clicking on the left/right arrows to copy the changes is a feature that I really like.
Below VS image is from Devart website, but in my case I setup Code Compare to open it outside VS instead of embedded, I think it behaves better. And in VS Options > Source Control > Subversion Environment
, I have this:

