It's all about looks. The Original Toothbrush is made from a hard cellulose plastic giving it an almost translucent "sea glass" appearance and the thumb grip will be smooth. The SCUBA is made from an opaque rubber and the thumb grip will have bumps and ridges. Also, when you push on the SCUBA's brush head the neck will bend and flex making it perfect for harder brushers.
Pick you favorite one here.
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The RADIUS Customer Service Team