Finding slotted screws is a bit challenging nowadays. I hunt and peck through a local industrial supply for the slotted screws. Usually they are plated in which case I throw them in some muriatic acid for a minute and then some gun bluing.
The saw tooth design cuts the threads very well. They allow a very good bite with virtually zero chance of splitting, square head design. I get the dry lube style with washer head. These are NOT Kreg's. They are a much improved design over the Kreg screws.
I don't like screws and use them only when it makes sense - securing table tops and the like. The McFeely screws are what I use.
If the screws are visible or I'm going for a certain period look then I will use brass or decorative screws. :gar-Bi