From the panel side, I’d say consistency is the biggest thing customers notice now. Cheap services get attention, but if they keep changing, dropping, or needing replacement, people move on pretty fast.
The panels that last usually win on reliable service history, realistic refill terms, decent support, and actually removing bad services instead of pretending everything is “premium”
Price matters, but reliability and a well organized panel is what keeps the client retention high. Some panels have started to include real drops stats, more advanced/custom algorithms for detecting real speeds, service performance...etc for highest reliability better to use from those ones, but its not a strict requirement. You can always use a normal panel, with due diligence, start small with several services panel admin has recommended, place some test orders and wait a week to see what stayed and what dropped(and what actual speeds were). Alot make the mistake of given into the trend and wanting to sell the latest service there and now, but long term, better to be patient.