People say that Senjutsu is similar to Haki because the sensing abilities in Sage Mode are just like Observation Haki since both abilities allow you to sense the presence of others and predict an opponets movements. Now I agree with them but after I thinking about, the natural energy that is used for the Frog Kata in a way is actually similar to Armament Haki. The reason I say this is because if you think about it both techniques involve using an invisible armor to increase a person's attack power.
Please don't fanboy about this and say which ability is better than the other. Actually take the time to read this and then think to yourself and tell me if this is all correct or not.