Whatever option you choose, the difference between having a number of simple Digital Display Screens in your stores tapping into a marketing system or several static menu boards that can be altered over a period of time is entirely your decision and should meet your requirements and circumstances.
With Digital it's a chance to take your signage from bland and outdated to a masterful selling tool that increases return on investment generating more eye contact. Alternatively you could also go for a more traditional look with static menu boards which are simpler and cheaper to install. The choice is yours.