+ True, pixel-accurate HDR with no backlight bleed or halo vs. MiniLED only having a limited number of variable brightness zones.
+ ultra thin
– Historically, OLED has has a burn-in problem - this doesn't seem to be a deal-breaker on phones, which have been using OLED for years, but its still a concern with TVs (OLED TVs have various mechanisms to defend against channel bugs, news tickers, info displays in games etc.) and maybe an unknown with iPads. All these things have different usage patterns.
~ May use PWM to which some people may be sensitive - but then so might a MiniLED or regular "LED" display.
In the end, it will probably depend on how good Apple's implementation is.
PS: OLED has actual, individual light-emitting coloured LEDs for each sub-pixel while MiniLED/LED are
LCD displays with a white LED backlight.
PPS: I apologise for all of the redundant and unnecessarily-repeated redundancies in that last sentence!