I think it depends on the context of the meeting. You can ask yourself questions like:
- How well do you know the person/people you are meeting? You will want to dress up a bit more if you don’t know the person well or have never met them to make a good impression.
- Where are you meeting? Their office? A coffee shop? Your office? A place like a coffee shop meeting is likely to be a bit more casual than a meeting at someone's office where it will be more formal.
- How does the person you are meeting usually dress? Try to match their normal level of dress. If they wear a full suit and tie all the time, you should dress to that level.
- What is the nature of the meeting? Are you pitching to them? Are they pitching to you? Is it a casual meet and greet? If you are pitching for their business, dress to impress. If it is more casual, dress more casual
I would generally err on the side of dressing up versus dressing down but I don’t think that every business meeting requires a full suit or dress. Rather, make a judgment call based on who you are meeting, the location, and the nature of the meeting.
That said, I think it is important to always look polished and put together. You will be judged on your appearance. If you are unsure, dress up, not down.
Also, how you dress can impact how you feel. Wear something that makes you feel good and confident and it will come across in your meeting.