SharpSvn was desiged for .Net 2.0 and Subversion 1.5 and later. It integrates all subversion dependencies in a single set of dll that is directly usable from .Net (XCopy deployable). One of the other strong points of SharpSvn is that it hides all memory management and transforms Subversion errors in exceptions, and more importantly vice versa. (Makes debugging callbacks very easy)
NSvn was used by AnkhSVN before AnkhSVN 2.0. It moved to SharpSvn after that.
The IronSvn project on Codeplex closed down. (It suggests using SharpSvn).
Svn# and its 2.0 successor Svn.Net are plain wrappers of the Subversion C api. They required the binaries of a subversion release to work. And you must manage the apr pools and some of the apr collection marshalling yourself from managed code. This is the only cross platform solution in this list. (Works just as well on linux)
