Knitting geek alert # 1

Having edited an abundance of knitting books by a wide variety of knitters for plenty of publishers, I've learned oodles of tips and tricks: some have become indispensable, others thrill my inner knitting geek, and some seem overly complicated for a not-very-good result. Now I'm sure that some of these tricks will be new/thrilling/indispensable only to me and actually well-known and rather dull to you, but in the spirit of knowledge shared...

Let's be entirely conventional and begin at the beginning with a slip knot. 

Images from Ultimate Knitting Bible by Sharon Brant (Collins & Brown)

1 With the tail end of the yarn in palm of your hand, wrap the ball end once around your fingers.
2 Slip a knitting needle under the loop around your fingers.
3 Wrap the ball end around the tip of the needle and pull a loop through the loop on your fingers.
4 Slip the loop off your fingers and pull on the ball end of the yarn to tighten the knot.

Does that look and sound familiar? It's the way most books show you to how to make a slip knot, and I made them this way for years. But as you have to tighten the knot by pulling on the ball end of the yarn, once you have cast on and knitted the first row it's impossible to easily tighten what will often be a loose first stitch (mine are always a bit baggy).

So I now make my slip knots this way.
 

1 Make a loop with the tail end of the yarn over the ball end.

2 Take the tail end under the loop.

3 Slip a knitting needle into the loop and under the tail end only.

4 Pull on the tail end of the yarn to tighten the knot.

This means that once you've knitted the first row, you can pull on the tail end of the yarn again to tighten the first cast on stitch should it be baggy. The only reason I can think of for not making slip knots this way is that the first stitch isn't locked off; theoretically I suppose it could come undone. I've never had an end work loose yet, and once the knitting is finished it'll be darned in, so it will be entirely secure. 

Does any one know any other reasons for not making your slip knot this way?