TBH the only benefits of Platinum that I've actually noticed are:
a) ability to get free Economy Space seats
b) a nice chat with a flight attendant when flying in Economy, sometimes with an early choice of food. When I fly in Business, flight attendants are blissfully unaware of my status

I've had 5 upgrades on 170 flights with Etihad so basically no noticeable impact on likelihood of being upgraded.