Why slotted?
If I remember correctly, when I was buying BBK a few years ago, drilled was for cooling, and grooved for removing contaminants, I think it mentioned that ultimately both these perks in brake discs were used on race cars which would dispose of their discs after one or two races. These perks on a road car give more probability of hair line cracks or fractures. So I guess its worth considering that if your going to do 1 or 2 track days a year, and do your majority of driving on normal roads, then new disc's, nice big ones, will be sufficient without the perks, and also cheaper...