Only you can be the judge of that. It all comes down to being able to find your way around the program rapidly, not having to spend countless hours trying to learn to use the software before you can actually go to work. All editors are different. Personally, I found CoffeeCup and Macromedia both lacking in that department.
Also, you'll find that most WYSIWYG editors lack support for some of the 'other' languages.
Besides, what makes you think that you need something more 'modern'? That could lead to you buying something just because you THINK it will work better than what you already have. If HTML Kit supports the languages you're interested in, it's good enough. The languages don't change much. If it doesn't support the languages you're interested in, check for an update/upgrade to the program.
If you really insist on getting something more 'modern', look for one that has a trial period. Try before you buy. That's the only way you'll ever know.