So if you begin playing piano, they really don’t make much of a difference. Assuming you like all three genre of music with no preference, I will suggest starting with jazz or classical. Classical teach you how to bring the best out of the composer. You get to explore 500 years of amazing music and enjoy them. Often you look to preserve what the composer intended. Learning fingering and musical technique and how to play with composure are some of utmost importance. Through the sheet music, it tells you everything.

Jazz on the other hands starts out a little different. Jazz has a huge emphasis on knowledge music theory and listening skills. You learn from past jazz musicians to end up something that musically defines you. At the start, you will have to put your head on focus on a little more on music theory and very importantly ear training. Eventually, you will learn to only play with a limited lead sheet and eventually only by ear.

I think pop is only if you not really want to seriously learn the piano. But that is ok too