You lag behind in development when playing the Nimzo?!? Really? If so, then I would probably avoid the Dutch if I were you as it is a far slower system than the Nimzo. In many lines of the Nimzo, one of Black's plusses is a lead in development in exchange for less space, bishop pair, etc., so if you are lagging in development you might want to take a different approach to that opening because Black is usually at least as developed as White, if not more, in the early stages...
What do you like besides endgames? Do you like playing against a pawn center? Do you like heavy theory? Kingside attacks? How important is king safety to you? Your answers to these questions will help determine which of the two defences would be a better fit for you.
Lately I have some bad results with my normal response to 1.d4, the nimzo-indian defense. I can behind in development and quickly my opponents are able to start a big Kingside attack.Therefore, I'm thinking about adding a new opening to my repertoire. The openings which I consider are the grunfeld and the Dutch defense.
Which do you recommend? Maybe it's usefull to notice, that my strong point (or least weak point) is the endgame. The sooner I get to an (equal) endgame, the better. The opening is by far my weakest point.