The WPF version has most of the features found in the WinForms SyntaxEditor. There are still some missing feature areas though, and we are working on knocking those out (parameter info, code snippets, smart tags, single line mode, and a couple others). We're wrapping up v2011.1 development now (which mostly focused on beefing up the .NET Languages Add-on) and then will begin on v2011.2 development and more of those missing core SyntaxEditor control features mentioned above.
Even though the WPF version is missing some feature areas, it also has a large number of feature areas and capabitilies that are not found in WinForms. Also many feature areas that are in both have had extensive new features added and improved design in WPF.