I've tried a lot of what's out there, and in the end Elixir and D'Addario NYXL stood out as being the strongest. You can bend these two more carelessly than the rest without worries.
But Elixir wins hands down because NYXL plain steels feel incredibly stiff, and just aren't any fun to play! With NYXL you'll be tempted to go down a size, and lose tone in the process.
P.S. Wound NYXL are very good, it's just the plains I'm not getting to terms with. They can definitely bend like champs, you just get the feeling they really don't want to! ;-)