Are there more 11 digit or 12 digit palindromic numbers?

There are the same number: any twelve digit palindrome is just an eleven digit palindrome with its central digit repeated. In general, if we are considering numbers of n digits: For even values of n, the number of palindromes is 9 x 10n/2 - 1 For odd values of n, the number of palindromes is 9 x 10(n-1)/2