effectuve firefighting sometimes requires brute strength. the 8lb would be more effective but like stated me being 5'5" 130lbs. im gonna get alot more of a work out thatn some of the other guys...(not saying im weak but just takes more effort)... this may be something to consider as to who you have for the job and what their physical capabilities and limitations are.---also the aplication of the tool it may at some points be more effective to have a smaller axe but for forcible applications like ventilation and such you have alot more power with the big toys.
try a 8lb flat head, next time you have a training whatever take it up on a comp roof and use the back side, totally destroy the roof. Great backup to the saw, and obviously is great for forcible entry. I take it in on almost every job. I toss it in a axe belt that I had custom made for it. If your interested I got it at www.traditionalfireleather.com Works awesome with all different kinds of axes, and even has a a lock to hold in a halligan if you want