Which type should I select for a filed contain user unique ID or thing unique ID?

In bubble there is a unique ID for users or thing and I can record them in the fields of any “data type”.
should I select “text” or “number”? I mean are there consequences for choosing either of them?

You could do text, but don’t store the unique ID, instead just store with the field type of your actual datatype. So if you want to store a “Invoice” under something then just create a field with the actual type Invoice

A field of type Thing itself.