I have been TripAdvisor/FlipKey for over 7 yrs. and get roughly 80% of my bookings from them with never even a threat of a charge back, so no complaints or concerns on my part.
When so many hosts report they have little to no traffic or bookings from TripAdvisor (or Air, or VRBO, etc.), I suspect it’s because certain locales or types of accommodation may be more popular with one platform than another – but who knows.
I don’t put any stock into the Air host guarantee (pshaw!) or offer any input in comparing TA and Air because I’m in a different situation from most. I am grandfathered in under the original terms/conditions of TA and am still allowed to manage bookings and payments myself. No service or booking fees are involved.
I pay an annual subscription fee and am provided with all the guest info (personal email and phone no.) in the first inquiry. There is no interference by TA or necessity to communicate with guests through the Dashboard, or sharing of the pie – which, of course, is the best scenario.
With Air, it’s less in my pocket, a lot less control, greater risk of refund or damage without compensation, forced requirements, etc. On many levels, Air is not the ideal platform for me.