To compare two decimal numbers, we look at the digits from left to right.

We compare the whole number part first.
Both numbers have a whole number part of 9. Since the whole number parts are equal, we move on to compare the decimal parts.

Next, we compare the digits in the tenths place.
In 9.11, the digit in the tenths place is 1.
In 9.9, the digit in the tenths place is 9.

Since 9 is greater than 1, the number with 9 in the tenths place is larger.

Therefore, 9.9 is larger than 9.11.

The final answer is $\boxed{9.9}$.
