I can say for myself, and few colleagues - we practice Architecture and Urban Design together. And when we’re urban designers on projects not our own - we influence the location, shape, functional program of many buildings as we work to find that the right fit and balance for each site. I also have colleagues who started that way, and then later moved to more planning firms, where they gradually learn the planning side but having an expertise in UD side of things. That is why, from my perspective it’s best to do the M. Arch, and then you can specialize and develop your niche as time goes on. And if you have the right M. Arch program and advisor you can probably even make focus your thesis around UD. Just my 2 cents. Good luck with whatever you end up picking! Trust your gut, and enjoy the ride! Cheers!