In reply to mattjohnson1:
As others have said, fit is the most important thing. I wear Scarpas - have used Mantas, Mont Blancs and Phantom Guides - but can't get on with Sportivas at all. Shame because they are great boots too! If you have the opportunity to try different types on then take it, it will be worthwhile.
B2 if you are planning on walking/ easy routes and want a bit more roll/ flex to the sole. B3 if you want to get onto harder routes. The bigger your feet are the more difference this will make. Lightweight is good, but they will last a bit less time so depends on your budgets/ how much you are going to be able to use them.
Again as others have said, worth considering crampon choice at this stage too and looking at the fit of what you want on the boots you get. Some boots with a very asymmetric sole or a narrow toe don't fit some crampons very well. If you can take your boots when you go to buy crampons/ take your crampons if you have some already to buy boots.