My son has extensively played with both (age 6). I have two recommendations. The first is if you have an iphone or ipad, buy that minecraft version as opposed to computer because there are no monthly fees and at the moment you can't play online with random people but you can connect two or more devices through wifi even if they are using the same apple account. This game can be addictive, but probably a phase like other people said. My son likes to watch YouTube videos to get ideas for new types of structures to build. It's pretty fun... We are building a lava palace at the moment.
Scratch is an awesome into to programming. We bought my son the book Super Scratch Programming Adventure (
http://www.amazon.com/gp/product/1593274092?ie=UTF8&force-full-site=1&ref_=aw_bottom_links) which I HIGHLY recommend. He got through 5 or 6 chapters and is now capable of making his own games. It's great! You can draw your own characters and stuff or use all the premade guys.
Both games allow lots of creativity.
