I had an inexpensive version of each, and I found preparing slides to be tedious, but my mother is a little anal, and always made me clean them and put them away afterwards, so I could never look at anything over time under the microscope. Culturing anything to look at was out of the question. If you are the sort of parent who will allow gelatin cultures of swabs ot the keyboards or phone or toilet seat, that could be endlessly amusing.
I liked looking at the surface of the moon through the telescope, once I figured out how to do that, but I didn’t have a map of it. If you go with the telescope, find out exactly what your child will be able to see, and buy some maps or star charts to go with it.
As far as which, I really can’t recommend. I would have been happy without either as a nine-year-old.
When I was nine, I wanted two science-y things: one was a human skull. It could be a cast, but it needed to be a realistic one. I think you can actually get casts where the bones are labeled, and they can be taken apart and put together like 3D puzzles.
What I wanted most that was science-y was an erector or some kind of building set with a real working motor, so I could make cars and cranes and things that worked. I wasn’t allowed to have one, because my parents thought I could somehow electrocute myself with two D-cell batteries.
I still love tinkering with electronics, and cars and engines, and anything like that. Lost interest in having a skull, but I did go and learn the bones in the skull once, when I was in a “memorizing lists” phase. I know all the presidents, too, and all the English/British/UK monarchs, beginning with the Conqueror.