Do my objects have too many sides?

[Sooshy77]

I'm making 10" funnel by taking a cone and subtracting a smaller cone from the interior. When I do this, lines appear that look like you can see through the funnel walls. If you rotate the image to the exterior side of the funnel, they are not visible at all. My questions are 1) Is having my sides set to 360 causing this issue? and 2) my work around has been to duplicate in place, rotate slightly, and merge. This "covers up" the holes, but I'm wondering if I'm going to get problems down the road when I actually go to print it.