The GW-7 does have a built in sequencer which can allow 16 tracks per song. So yes u can create your beats in the GW-7. Im not sure if it has a loop feature or not.(download manual and read if thats an option you are interested in.)
The Juno D seems to be nice and i like that it offers computer software for programing your own sounds.
But i just recommend u read all the fully detailed specs side by side and then go with the one that offers more for what u are looking for.
Write down on a piece of paper what u want to be able to do wit a keyboard then start researching.
Nicole