jmc

The largest power of 2 less than 1200 is $2^{10}=1024$, and the largest power of 2 less than 200 is $2^7=128$. So, we know that 1200 in base 2 will be a 1 in the $2^{10}$ place followed by other digits, and 200 in base 2 will be a 1 in the $2^7$ place followed by other digits. Since $2^{10}$ is 3 places away from $2^7$, 1200 will have $\boxed{3}$ more digits than 200 in their base-2 representations.