Silver's Sock tutorial question

When you are knitting down to start the heel and you will be knitting 32 rows. On Silvers class it says to slip knit slip knit one row and slip one and purl across on the next row. I have been using the Knitting Pure and Simple directions and it has you only slip the first stitch of each row. I was wondering what the difference was in the finished product? Thanks!!!

you are making a stronger heel. it looks super cool. just trust silver. her tutorial is da-bomb.