“I don’t care, you decide” isn’t the name of a restaurant.

You may think you’re being nice or accommodating. It doesn’t always land on the other person that way. More often than not, your flexibility is unkind.

You are leaving the mental work to them – to make the decision that impacts both. They are then left with trying to guess what you would like. Sometimes this also means that they also have to do the research and planning. If you say this often, then you are leaving a lot of heavy work on the other person.

Here are some ways such words might come across:
The other person might get a sense that you do not have an interest or investment in the situation; it can feel like you are slacking in the relationship. They also may not like to have to make all decisions that impact both of you; they may want you to take care of them sometimes. They may get a sense that you are afraid or insecure about your opinions, and they want you to be more confident.

Also consider that by not sharing your preferences, you are not allowing the other person to get to know this part of you.
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There are better ways:

• If both options are good for you, then just pick one. Take on the responsibility of making the decision.

• If you really think that in this case, the other person should choose, then allow them to make the decision but help narrow it down. “I’m thinking that we do more casual tonight. But if they make a decision, then there is no going back and forth.

• If you really have some preferences, then ask for time to consider what you’d prefer. “Give me a few minutes to think about what I’d like.”

• Decide together that you alternate making this decision. One time, you choose the restaurant and the next time they do.