A breath test is sometimes better than a blood test because its less reliable. Whereas, a blood test is very hard to dispute scientifically. If the police are relying upon a breathalyzer, the evidence can be attacked on the basis that the officer may not have properly calibrated the device or failed to properly administer the test. Under Nevada law, a person “may refuse to submit to a blood test if means are reasonably available to perform a breath test.” If you refuse to take both tests, the police can get a search warrant from a judge and force a blood draw.