Which is better, TutorWyz or Preply?

They are different kinds of thing, so it depends on what you need. Preply is a marketplace with thousands of tutors across many subjects and languages — better if you want breadth of choice, a very low entry price, or a language taught nowhere here. TutorWyz is one named teacher rather than a catalogue: the same person assesses, plans, teaches the classes and writes the monthly report, across grades 1 to 12 in IB, Cambridge IGCSE and A-level, AP, CBSE, CISCE and NIOS, with a few well-qualified part-time teachers only as cover for the hours she cannot take. If what went wrong last time was a tutor who changed every term, that difference is the entire point. If you want to browse and compare dozens of profiles, a marketplace genuinely serves you better.