Vijay Govindarajan and Mark Sebell in their HBR article Match Your Innovation Process to the results you want very precisely tell you when you should use top down and when you should use bottom up approach for Innovation in your organization.
Ideally you should have both going on in parallel, bottom up for incremental innovations, and top-down to find that magic wand that can change the fortunes of your company.
There is a need to understand that these approaches complement each other and complete the spectrum of Innovation in your organization, and they are not mutually exclusive or a matter of choice for the organization. It is possible that at a given point in time for the given situation within the company or in the ecosystem you may choose one over the other, but in the longer run you need to have both running in parallel and giving you a constant supply of ammunition to aim for larger top line while all the time improving ways to strengthen bottom line.
If you are asking this vs that question, that means you have not really understood the purpose of both the approaches.