i'm wondering why when you mention your props as 6-5 or 6-4 nobody seems to weight their props. I would think 2 6-4 props with different overall weights would spins differently?

Jim,
To first order, weight doesn't really matter very much--unless you are making them out of depleted Uranium!. It is true that it will take longer for a heavier prop to spin up (this is just rotational inertia, aka flywheel effect), but once up to speed, you are basically only having to provide energy for thrust--weight no longer matters. It is true that a heavier prop will have a larger gyroscopic effect than a lighter one (everything else being equal).

That being said, for the most part, electric props are also pretty light. They are quite thin compared to standard props used with glow engines. The main reason for this is that an electric motor provides much smoother power pulses to the propeller, many for example for one complete revolution, whereas a glow engine gives you one big pop per revolution. That means the glow prop has to absorb a large kick and therefore needs a thick root and blade. So since the electric prop is thinner, there is less material. Also most of us use the prop designation as an identifier---so if I say I use an APC E 6-4, you know exactly what prop I am referring to.

As Mark says, different manufacturer's 6-4's (for example) may behave a lot different. But once you find one you like--and it performs how you want, then you stick with it.