From what I understand, being arrested at the U.S. border while entering the country is strictly worse than being arrested while inside the U.S. In the latter case, the police arresting you will at least read you your Miranda rights, will have no right to search your phone unless authorized by a warrant, and will generally offer bail to get out of the jail in exchange for a court appearance. That's what due process, at a minimum, entails.

None of that happens at the border.

At this stage it doesn't even matter whether you have broken any U.S. law or not.