Definately let the wood take the weight. You can use screws, and might even get away with it indefinately, but ........... you might not. If this type of stand fails, you might see it before there is a problem, but you might not.
There, is that definite enough? lol Seriously, you will find very few here or on any other forum that will advocate anything but wood on wood. If it is well designed and half way well built, it will outlast your tank.
Do you have a design in mind, or are you still looking?? (hint, hint, folks).