Check the LocalContentStatus property on the statuses, here is an example:
var statusArgs = new SvnStatusArgs();
statusArgs.Depth = SvnDepth.Infinity;
statusArgs.RetrieveAllEntries = true;
Collection<SvnStatusEventArgs> statuses;
svnClient.GetStatus(@"C:\SVN\stuff\", statusArgs, out statuses);
foreach (SvnStatusEventArgs statusEventArgs in statuses)
{
if (statusEventArgs.LocalContentStatus == SvnStatus.Modified)
Console.WriteLine("Modified file: " + statusEventArgs.Path);
}