I agree that iMovie and WeVideo are great options (haven't tried Splice yet.) Another platform that we use in my district (www.bwrsd.org) is Adobe Spark Video.  It is a high-quality tool (works on all devices) that has built-in templates and stock media which helps cut down on the amount of time students spend curating material and editing.  The Post and Page features of Adobe Spark are also great ways for students to creatively demonstrate their understanding of an issue and communicate that out with an audience beyond the classroom.  Reach out at any time with questions: Twitter @mr_driscoll.  Websites Tomdriscoll3.com and moderncivicsproject.com