Well, not that serious. And people do like both, but most of my friends and family seem to prefer one to the other.
Both udon and soba, of course, are noodles. However, udon is a wheat-flour noodle, and soba is a buckwheat-flour noodle. So, they're quite different as far as noodles go.
There are various ways to eat both noodles—hot and cold. Recently, I was in Izushi, Hyogo Prefecture. It's famous for its soba, and the Japanese royal family visited *somewhat* recently.
Above you can see soba being made by hand. There is also a tray of soba noodles. The noodles are in little plates, which is why this is called "sara soba" (皿そば). You crack open an egg, add wasabi, green onions, and tororo (a gooey substance made from yam). Then you dip the soba in this mixture and eat it. While I'm definitely an udon man, it was quite delicious.