When comparing Qt vs Tk, the Slant community recommends Qt for most people. In the question“What are the best cross-platform GUI toolkits?” Qt is ranked 2nd while Tk is ranked 9th.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Open-source
Pro Global community
The community behind Qt is both massive and approachable. Digia (also owners) are joined by the likes of Intel, KDAB, ICS, Canonical and numerous others in sponsoring development, while communities such as KDE also contribute significantly. Forums are active, mailing lists are open, irc channels chatting, git repositories well managed. Answers to questions are usually minutes away.
Pro Good documentation
Professional, thorough documentation with examples, available either in a web browser or in the stand-alone desktop client called assistant.
Pro Easy styling
Once you understand how to style, the styling can look great.
Pro Great for beginners
Easy to pick up and run with it.
Pro Easy and good looking in Mac, Linux and Windows
Pro Bindings for several languages
Bindings for Python, C, C++, Ruby, Perl, Go, Java, Haskell and more, see Languages with a Tk binding.
Cons
Con Base looks are garbage without a good amount of styling
Going with the base look for your app is a bad idea because it looks like garbage with the defaults.
Con C# support lacking
Although the Eagle Project exists, which offers Mono and .NET Core support, C# support is not standard.