Why is Trezor better that just using Bitcoin Core on a laptop?
Because Trezor is effectively a cold wallet; it doesn't expose your private keys online ever. It's been invulnerable to remote attacks so far.
Bitcoin Core is also safe, but because your keys are stored in an online device (though it can be used offline), it has more possible attack vectors.
It appears to me that Trezor offers smaller attack surface which is great. Am I correct by ordering these by safest first:
1 - Cold storage (i.e. paper, usb in a safe) only for long term storing
2 - Trezor
3 - Bitcoin Core
with a trezor, even if you wanted, you can never know the private key, nor can any computer or virus or any other person!
a piece of paper or an usb is safe aslong as the entire process of generating your key and writing it down, was done properly. it's simply easier and much more convinient to use trezor, but it also costs.
I wrote some more about this
here