The major difference between drum and flatbed scanners will be noticed on photos that require fine detail or subtle gradations in shadow areas.
Flatbed scanners have a limited dynamic range.
Unfortunately, there is no easy answer as to how well each scanner will work due to things like the quality of the original, quality expectations, and operator experience. For assured high quality use a drum scanner. For most color work a positive transparency or slide is best. If the original is a large reflective piece of art, such as a water color on paper, it must be flexible to wrap around a drum. Color negatives are not good for scanning, photographic prints should be made as they reproduce acceptably.