I am in Canada and picked up some scrap 3/4" MDF at Lowes to practice on. Did a few signs and the finished carved faces were super smooth after using a 60 v bit, did not have to sand anything. Next I picked up some MDF from Windsor plywood. After carving the finished surfaces are noticeable rough. You can actually see the tool paths. I have to sand everything but this is very tedious and does not produce the same finish as the initial MDF from Lowes. I have sharpened my v bit and check all the settings. Even tried some superlite MDF but got the same result. Realize that Lowes and Windsor probable source their MDF from different sources, and the Windsor MDF is softer in the interior layers. Have gone back to Lowes and picked up some more MFD but have not carved it. Anyone have the same issue? Has anyone ever tried the moisture resistant MDF, is the interior hard?
Can’t speak for the difference between the two you bought, but its the same with any wood. You can buy a couple pieces of walnut from the same mill and each board could give slightly different results on the finished produce after running it on the cnc. Now two pieces of wood are ever exactly the same, and I’d bet the same with MDF. I have some fuzzies on the edges of MDF sometimes, sometimes I don’t even with a new razor sharp bit.
One things you could try with the MDF is sealing it before carving. That might help you if you think the MDF is too soft.
Are you doing two stage carves on it? I use MDF often and have seen toolpaths when I don’t use the same exact spot to probe. This will affect your work, especially if the MDF has a slight warp.