Check Wikipedia or any other site for more info about them.
The first to enter the real interactive entertainment was Sony with its PS2 peripheral the Eye Toy with motion sensing and other capabilities so NATAL is actually nothing that much new especially that Sony updated its Eye Toy to the PlayStation eye(On PS3) with more advanced 1:1 motion sensing and higher resolution and frame rate recording. But Natal will need your full movement and gestures to give output from the game while the Move is still a Nunchuk and Wiimote on PS3 so the Natal will need you to be an athlete to play hardcore games and as we know hardcore gamers aren't usually athletes.
I see Natal as a completion of PlayStation Eye and Move as a completion of the Wii. So both aren't really that much interesting but people who have any of these consoles will buy their peripherals depending on their interest in the peripherals games. But one major mover is the Milo and Kate game that needs NATAL to be played and i have seen some videos of it and it is great with lots of innovation based on a project by Lionhead studios in 2001 code named Dimtri or "Emotional AI". Just a hint for is that Milo can know if you're sad or happy and he'll ask you why sometimes he'll ask you to draw for him. Try to be his mom and ask about his homework and he'll answer differntly anytime you ask!
In conclusion i see that both will have their success in the gaming market and may attract some non-gamers to buy these consoles just like the Wii did before.