I think the hard dentin is worse one,

hi, hot or cold..... vital teeth have sensors plus oral cavity is richly supplied so its not a wide range. enamel is the outer shell and protects the underlying dentin. infect dentin is the stress absorber for enamel. i hope you ill find this article helpful

https://doi.org/10.1016/j.jdsr.2015.07.001

I think if you drink or eat very hot or very cold foods this will cause a crack and may a danage of the tooth.

I think the cold things are more harmfull.