There's no color like black.
I don't subscribe to the arguments about black as summation of all color, nor to it being the total
 lack of color- not for painting at least. It is, however, a very unique, dissociative, color with
zero chromatic strength and incredible value strength. Once employed, all color must answer
its presence. There are schools that called to abolish it from the painter's pallete, and then there
are artists like Picasso who used black as a brazen torch to elucidate his eloquent vocabulary of forms.

So why 3 different blacks, they all look the same to me?
So here's the fun of it: Which one feels better?
Not in the hedonistic pleasure sense, but in the shoe-size sense.

Ivory Black is the long standing staple of traditional painting workshops. It is made
of charred animal bones (usually cows from the leather industry) and is fairly warm in tone.

Mars Black is an iron-based pigment (named after the Roman god of iron) and
is characteristically robust. A bit cooler than Ivory, an excellent all around pigment in
terms of durability, opacity, longevity, and color.

Lightfastness ratings: 1; all semi-opaque.
Bound in alkali refined linseed oil.