Size is the most crucial factor to consider when picking out a pedalboard. Not only does your new board have to fit your existing pedals, but we recommend giving yourself room to expand. You will most likely purchase more pedals in the future, and you don't want to buy a new pedalboard each time.
Also, don't forget about your power supply. The power unit needs to go somewhere, and whether that's underneath or on top next to your pedals, remember to account for the space it will take up.