Whichever one fits your foot best. Try all of them on, if you can!
Matty, keeping snowboarding simple around here since Nov 2010....
Also, if you're looking at price points, consider how many days in a season you're going to put on them. Some lower end boots will last 30-50 days (or less) while some of the more expensive boots will last 70-100 days (or more) before parts (outsole, laces, etc) start breaking.
In the end, follow _stark's advice. Having a great time sliding on snow starts with some boots that will be comfortable for the entire day.