This study compares different acoustic metrics suitable for characterizing distortions in the articulation of vowels in the speech of dysarthric speakers with ASL. Metrics are tested for their performance in distinguishing patients vs. control speakers, and according to their relationship with speech intelligibility and perceived vowel alteration. Results support the need for different acoustic metrics in order to capture the large inter- speaker and inter-sex variation observed, and to reflect the various types of alteration possible.