It depends on what makes you happy. If you only typically eat 2 meals a day and don't do signature dining venues often, then downgrading your dining plan and getting the concierge benefits could be a good fit.
However, if you have a family of foodies and tend to use most of your Deluxe Dining points, then it could actually end up being more expensive because of the additional out of pocket expense (or it could make for some unhappy family members).
Benefits of Concierge
-greeted upon arrival and escorted to check-in in the concierge lounge (usually)
-use of concierge to book meals and extra activities (rumor has it they are subject to the same restrictions as booking meals online yourself- so you still need to let them know your preferences early, and if something's gone, it's gone. However, they may check for cancellations for you and get you in)
-use of concierge lounge, which at GF is mainly about the snacks. You get continental breakfast items and yummy treats in the evening. If these snacks sound more appealing than a full meal, have at it.
Personally, I would stick with the Deluxe Dining, but since it seems like you visit Disney World fairly often, so if you want a different experience at the Grand Floridian, it could be a fun change of pace. Some people swear by concierge and will never go back. Others don't feel extra special or pampered with concierge and therefore don't see the point in the extra cost.
I would see what your family members want to do.