No clear winner - they both have advantages over the other. Verbling has more control over the way lessons are taught by providing lesson materials, and uses their own proprietary platform to connect the teacher and the student. italki on the other hand has more flexibility with more teachers, and the option to use any software to conduct the lessons (Skype, Zoom, Whatsapp, etc.) As they are both service-based platforms with real people, the true value will be trying different teachers until you connect with someone who you feel will give you the best tuition to suit your personality.