Separate, unfortunately for your wallet... This one's a proper 3DS application, whereas Petit Computer is a DSi application that was carried over to the 3DS eShop.
That being said, I don't think the new version will run programs made in Petit Computer as is without a fair bit of tweaking, so you do have the benefit of being able to try out the Petit Computer programs already made. It's not a complete waste!
That being said, I don't think the new version will run programs made in Petit Computer as is without a fair bit of tweaking, so you do have the benefit of being able to try out the Petit Computer programs already made. It's not a complete waste!