Patching and Plastering - stucco next to drywall, how to "finish"?

We have an interior wall with plaster and button board on one side but stucco (it was formerly an exterior wall) on the other side. We are closing up the old window opening on each side with framing and drywall. I think I'm okay using drywall joint compound and tape to seal it up on the drywall/plaster side, but what about the drywall/stucco side? What do I use to form the wall surface when these two mediums are side by side? (Something meant for drywall, something meant for plaster, or not stucco I pray....?) How about texturing on each side? Just experiment with the 9" or 12" blade? help!

If I understand correctly you have 1 wall with stucco that you are patching and 1 wall with plaster. If so I'd use a setting compound [like durabond] to do most of the work. It dries harder and shrinks less so you can get by without taping from the drywall to the other types of surface. You should be able to duplicate or mimic the texture finish with joint compound although it may take some experimentation to get the texture right.