Big, I pulled about 4 osage bows out of the garage the other day just to check a few things, the heaviest bow is 67# and is also the norrowest and has the highest mass weight. The lightest bow is 48# and is physicaly the lightest bow but also the widest and largest physical demensions.
Idealy when you select a design for your bow you incorporate that into the tiller, A pyramid bow should pretty much have an arc of the circle tiller, where a bow with paralell limbs for a certain distance should have a more elyptical tiller. Lets say you made the first 16" of the limb paralell but when you tillered it you tillered a nice arc of the circle tiller. Your mid limb would be stressed far less than near handle wood, this will give you more vibration in the bow and possibly more set near the handle. Thats one of the reasons I started using mass to dictate my demensions for a bow, just too much variance in wood density. I like and use both designs you mentioned but more based on how much wood I have to work with. A pyramid bow will carry less mass but will not neccessarily be faster.
If I was going to make a firstname.lastname@example.org" pyramid bow I would want it to weigh at least 22 0z, If I was going to make a paralell limb bow of the dsame length and draw I would make it 25 oz with an elyptical tiller. Steve