As someone who is Level 3 trained in Internal Family Systems, in Somatic IFS (McConnell), in Trauma Informed IFS (West), and who has been a Level 1 Program Assistant with IFSI, I have found Relational Intelligence to be a much more systematic and powerful model with regards to working with clients who have a difficult time unblending from parts.
I have also found RI to be a much more powerful model than IFS in working with pre-verbal trauma and somatic traumatic memory. Dr Le Doze provides a very clear, useful and neuropsychologically sound protocol to direct the use of practical interventions far beyond those taught in any level of Internal Family Systems.
Clinically, I find Relational Intelligence to be a far more useful and effective model than any other in my work with clients dealing with complex trauma, chronic illness, chronic pain, and cancer.