It may also have to do with the difference in the way that the top was decreased as well. The pattern I had used in the past decreased something like: "K4 K2tog" all the way around for 4 rounds and then "K2 K2tog" for two more rounds, etc. The decrease for these mittens was something like this (I do not have my pattern in front of me so this is all from memory): K1, K2tog, K(x number of stitches), K1, SSK, K1, K2tog, K(x number of stitches), K1, SSK. The first way creates a rounded top whereas the second method creates a more angled look. Compare with my other recent mittens in a prior post here.
I used my trusty Knitting Answer book with me to help me with the three needle bind-off, but if you'd like a video demonstration, be sure to check out Knittinghelp.com. To do this for the mitten, I turned the mitten inside out so that the right sides were facing.