UA and AA Dining - some restaurants in both the program
 

I signed up for the AA and UA dining program and I was trying to find restaurants from both the sites. It appears that most of the restaurants are common to both the programs. I found this particular Caribbean restaurant and it is in both the dining programs. Will earn miles in both the dining programs? I registered my Amex card in both these promos.
It would be great if I earn in both the airlines dining programs.

Most dining for miles restaurants are program agnostic, although not all.

In response to your question, you will receive miles in whichever program your card is registered at the time of processing. You may be a member of both American and United but your credit card can only be linked to one program at a time. Without making further changes, you are set to earn miles in the plan you registered your card in most recently.

It used to be that it wouldn't let you register a card in a second program. Recently they changed it so that it's automatically deregistered in the first.

The same company operates most of these programs: these two, Delta's and a few more. When a restaurant signs up to be listed, it's generally in all of them. It will only give you one serving of miles. No seconds. Sorry. Mother knows best.

There is an entire forum dedicated to these dining progrfams here on FlyerTalk:

iDine/Rewards Network forum

That is where you should ask questions about how they work (and, in fact, once you look around, you'll see most of your questions have already been asked and answered).