I'd say MArch. Once you're done with core studios, take urban design studios. MUD is basically a combination between MArch and MUP, personally a 60/40 mix. You already have a planning background, so why not focus more on what you're lacking unless the title of the degree matters? Landscape architecture is a whole different field my friend. An architecture or urban design program would just lick on its surface.
Do MUD, you can learn both.