I wouldn't say the Shack and TKZ are in competition. The Shack was born when TKZ closed in April 2002, MrG was rpg code manager at TKZ and I gave him the TKZ rpg code resources to start his own site so everyone could still download them. And Spyder did offer TKZ all of the Shack resources, but I refused, even though a lot were off the old TKZ.
So TKZ isn't really here to compete. I think TKZ is the place for tilesets, MS for games and the Shack for coding.
Of course, with MrG...who knows what'll happen with the Shack in the long run.