Personally, I chose OT because I preferred the setting OTs work in. When I began shadowing at rehabilitation facilities, I appreciated that OTs work in an environment where they have time to get to know their patients and work with them consistently for longer periods of time. I also liked that OTs primarily work with patients with injuries or disabilities - it seems that with nursing you might work with a wider variety of conditions.
Have you been able to shadow both OTs and nurses? That would give you an idea of what roles they each play on a daily basis, and would give you the opportunity to ask questions about different jobs within the field.