Ledger supports a huge amount of coins/tokens when compared to Trezor and a trezor wallet is been made up of plastic whereas a Ledger is made up of steel which increases its support for good quality. Ledger on the other hand uses the 4pin setup which further increases its security.
According to a user above after the release of 1.4.1 there has been too less possibilities of down time or software being slow for accepting too much of currencies. Since a 4 pin setup is done by you, a hacker must know the pin to send crypto from one wallet to another.
When you are ordering a wallet, the wallet is taped so that when it is altered, you can contact the support team so that you will not be phished. Ledger has a important addon such that they can be setup without being plugged to a computer which even increases your privacy further.
You're wrong with number which is available for the pin,it can be minimum 4,but even in previous version of Ledger firmware user can set up to 8 digits.I think that number of 4 digits is quite enough because after 3 wrong pin device will reset and wipe out everything on the device.However 8 digits are extra security for users,even though it is a small probability that someone will guess 4 number in 3 attempts-it is even less probability to someone guess 8 digit password.