Which is more accurate and which probably came first in the time line? I also would like to know which is more useful to scientists and overall?
The big shortcoming there is that many people would rather be wrong than uncertain, and many people deeply resent anybody questioning the basis of something that has already been accepted. About twenty years ago archaeologists did not dig below the 9,000 year level because it was forbidden to find anything older than that. There was no particular reason for that, the authorities simply declared that humans had not been in the Americas until 9,000 years ago, and it was professional suicide to question that or to find anything that refuted it. Kennewick Man was found and got a lot of stories in the news before it was determined that he was 10,000 years old. The authorities were forced to ease their restriction. Right away more evidence was found of humans in the Americas 15,000 years ago, then 50,000 years, and now it is ok to find evidence of any age in the Americas.
All dating methods are based on shaky assumptions. Radioactive decay is known to be randomly affected by electric currents. Relative dating means fossils are dated by the rocks they are in, and the rocks are dated by the fossils in them. That is called "swag", which means "Scientific Wild A@@ Guess". If you ask a scientist about any of these things, he will shout insults at you until you go away. Science nowadays is anything commanded by the scientists that control grant funds. They are very strict and in some topics totally wacko.