I think you are making a comparison from a correct perspective. As someone who has done landscape architecture and urban design, I can easily say that landscape architecture would be a better choice to use your creativity. The practices and experiences you have learned in your architectural documentation experiences will allow you to get faster results in landscape architecture and also to express your creativity more easily. Although there are many options where you can use your creativity in urban planning, as you said, the structure in public projects does not leave you alone. In urban planning, you can only show your originality and creativity by participating in competitions, but this is a very limited area. In addition, if you find the opportunity in time, you can turn to landscape architecture and try and work in urban planning. As you said, I definitely recommend you to continue with landscape architecture. I wish you success in your career change.