A hot oil treatment enriches the scalp and hair especially when using oils with penetrating properties. The oils contain essential fatty acids (EFA's). The sebum produced naturally by the scalp also contains EFA's. EFA's can help porous and dry hair become more soft flexible.
Moisturizing conditioning treatments contain humectants that help keep up the moisture level in the hair which also makes hair softer and more pliable.
A good treatment should contain both. That's why one of the best ways to enhance a mediocre conditioner is to add some extra virgin olive oil (high in EFA's) and honey (humectant).