'Scarlet' is really the first time U2 tapped deep into their gift, kind of the doorway into the future of U2. It encompasses everything U2 would be sonically, in a sense shining through the prism of U2. It's a gorgeous piece of music, depicting the tap drumming, the minimal guitar picking--the first sign of the "silver" sound in Edge's playing--and a hypnotic and spiritual vocal. This is U2 at their most innocent...and looking straight into themselves.
So yes, I pick 'Scarlet'.