I will stick with the diamond awl Dennis. I was taught that the center of the diamond is the opening for your needle point to pass through. Then pull back opposite the direction of progress and the first thread tucks back into the back end corner. This leaves way for needle number two to go through the hole without catching/nicking the first thread. Then I cinch both ends up. The thread wax holds things steady. Then on to the next hole. My take would be that a straight slot makes passing the needles through harder, and to no advantage. In some difficult areas I can see the straight slots being a serious disadvantage. I was also taught that a diamond awl hole will close up and become invisible when the stitching is hammered flat (seems to work). Not sure about a straight slot hole. I am certainly no expert, so take my thoughts for what they are worth. Between my dad dying a year ago, cleaning out his house for 11 months, and my own house catastrophe 3 months ago, I have had no time or access to equipment for leather working. God Bless, Marc