You're correct that the planer can remove much more material at a time. With the planer, it is also simple to adjust the depth for removing more material in a pass. With the drum sander, you can change the grit of the paper to take off more material (nowhere near as much as the planer) but that is a more painstaking process.

That said, I own a drum sander but no planer. I used to make acoustic guitars and work with figured wood. In this case the planer is of little use since it will take out chips where the grain angles up. The drum sander does not chip-out the stock and allows smooth and uniform surfacing of wood down to 2 mm thickness, even thinner if required.

So, preference rather depends on what you're doing. I've also used my drum sander to fashion oak window jambs and trim. It required more passes than a planer would have but I would have wanted the drumb sander for finishig anyway, I was happy with my choice of tools.

You're correct that the planer can remove much more material at a time. With the planer, it is also simple to adjust the depth for removing more material in a pass. With the drum sander, you can change the grit of the paper to take off more material (nowhere near as much as the planer) but that is a more painstaking process.

That said, I own a drum sander but no planer. I used to make acoustic guitars and work with figured wood. In this case the planer is of little use since it will take out chips where the grain angles up. The drum sander does not chip-out the stock and allows smooth and uniform surfacing of wood down to 2 mm thickness, even thinner if required.

So, preference rather depends on what you're doing. I've also used my drum sander to fashion oak window jambs and trim. It required more passes than a planer would have but I would have wanted the drumb sander for finishing anyway, I was happy with my choice of tools.