In reply to Salm0n:
As normal, people are making slightly sweeping generalisations (or possibly making sexist assumptions given your limited profile).
Boot stiffness probably depends more on size than B2 or B3 rating. If you've got tiny feet as some female climbers do, you could probably climb WI4 in boots nominally rated as B1. Equally, if you've massive feet, anything except the absolute stiffest of B3 boots are going to feel hard work.
Additionally, climber weight may make a difference; a 16 stone mountaineer might want stiffer boots than 8 stone sport climber even if they have the same size feet.
However, unless you are very light or have small feet the advice of going for B3 for ice climbing is fairly sound.
Post edited at 16:43