In your opinion, what is more important for restaurant atmosphere or food/drinks quality?

We can assume you have just one of mentioned advantages, so scenarios are as follows:

1. You have good food and drinks and bad atmosphere - if your restaurant has such menu like no other, if it is at such place where customers are changing fast (airport, hotel) - then it is not so bad, anyway they will not come back or just forget bad ambience. But if your restaurant has food like any other place or there is a chance you can get regular customers - without ambience it's hardly to believe that they will come back.

2. You have good ambience but food/drinks is not good - I have such places where I come back although food/drinks are not so good and I order the most regular drinks there which practically can't be spoiled - like black coffee, gin&tonic, coke. There, usually I read books, magazines or just simply enjoy.

Surely, it's easier to prepare good food than create good ambience.

Depends, but better if you have  both!

If you don't  offer both maybe you aren't on the market right now. We have a big competition in UAE at list in my area.

Regards

Jordi

It is a personal preference. I would suggest, food and drink is far more important than atmosphere if eating food is the main course here in this discussion.  Especially, when added value. YOU GET WHAT YOU PAY FOR. Not to ignore customers 

Not to ignore customers needing entertainment, then atmosphere would be more important.   As a result, we must know customers needs and wants in order to segment our clients. 

 If I have chosen to go to a restaurant in particular, I already know that I like the food, so the rest of the ambience success depends on the service and the atmosphere.  

I like to be attended to often and checked on to make sure that I am satisfied.  I like to discuss the ingredients of the food with the servers/chef and make suggestions.  I want my food to look like the pictures on the menu, and the small extras (like condiments) to keep coming.  I can be pretty demanding because I really want to enjoy the meal and the evening and the company of my friends, but I also acknowledge service well done and try to let the servers and manager know as well as tip accordingly.

I think both factors. Another vital thing is a conception. Restaurant must have its own style, which is different from others. There should combine coziness, fun, delicious and unique food, original drinks.

Both (food/drink and atmosphere) and pay also attention to the illumination...is so rare find restaurants with cozy illumination (always "cold" and too bright!)