Both. I'm just thinking if you have one lam that is inconsistant (maybe a knot, soft spot, etc.)then 50% of your lams are inconsistent in a 2 lam bow. If I was only going to do a 2 lam bow then I would use action wood or action boo(flooring) because by the nature of them they are consistant.
For a 64" 55# longbow your 2 lams would have to be pretty thick. For my hybrid bows that would be about .150 each with one being a taper.
A 4 ply piece of plywood would be stronger and more consistent than a 2 ply piece. Although I know bows and plywood are not the same thing. Chad