The 6" steel well is a mainstay in Wisconsin due to the fact that it is a requirement for potable wells where the casing terminates in a consolidated formation (bedrock---Sandstone, Limestone, Dolomite, Granite, Quartzite, etc.)
This well can be screened or have lower open hole in the bedrock from which you obtain your water.
Anywhere that you drill in Wisconsin, if you drill deep enough, you will get to bedrock sooner or later. Sometimes it sticks of of the ground in outcroppings that we can see as we drive down the interstate or visit Wisconsin Dells.
The water quality can be better, worse or the same as in the upper unconsolidated formations. In our area the TENDENCY is better water quality in the unconsolidated formations but it is very dependent upon the specific location.
Typical 6" well with Baker Turtle Vermin-proof Well Cap
In areas where the bedrock has high iron or other issues, water quality can often be improved by installing a PVC liner, insulating the steel from the water.