According to Colorado DUI laws, your blood alcohol level will generally determine whether you can be charged with DUI or DWAI. If your blood alcohol level is greater than 0.8% then you can be charged with DUI. If your blood alcohol level is between 0.5% and 0.8%, then you can be charged with DWAI instead.
In both cases, the only factor that matters to the prosecution is your blood alcohol level!
Your driving ability and field sobriety test performance are completely irrelevant to the prosecution. Either your blood alcohol level exceeds the limit or it doesn’t.
A refusal is almost always charged as a DUI.
In almost all cases where there is a refusal to take either a blood or breath test to determine the level of alcohol, you will end up charged with the more serious offense of DUI. Again, to the prosecution, they will not care about these other factors but will simply assume since you refused a test that you were driving under the influence.