Being a woodworker for all of my adult life, I would tend to use maple for the turning. It has a fine grain and will give a smoother product than oak. If you use oak and want a smooth finish, it will need to filled with a wood filler before applying the finish. The cherry will fall between the maple and oak. It is a very quick and simple turning for anyone with a lathe, maybe 30 minutes.
I want to add something to the above post. All maples and all oaks are not the same. But for simplicity since these are to be painted, any close grained hardwood will work well. Oak, especially red oak is not close grained. Hard maple, Walnut, Cherry, Birch, etc, will all work well.
Also, a baluster, cut off, will work Ok, but only if you can find one with the right diameter and taper. I would not be that lucky.