If we take an 8 character password which is composed of 3 lower case, 3 upper case and 2 digits we’d have a password that gives about 30 billion combinations; while if it were to be made of 2 lower case, 2 upper case, 2 digits and 2 special characters that would make about 45 billion combinations

More than that, anyone trying to brute force your password might actually not include special characters at all in his brute force set due to the bigger timescale required, thus it would ensure that for that attack your password cannot be cracked at all.

That being said length is obviously your ally as well. In order for a brute force attack to crack the password given in the example: Mc2322UtPaDnW2D an attack needs to be configured to go through 14 qunitrillion combinations (thats 10 to the power of 18). If one adds special characters to this password it can be shortened by a couple of characters and keep the same number of combinations, so just see what’s easiest for your users to remember. In any case both passwords will need 1000s of years to brute force so one should be pretty safe there.