Smiles still more worth it. Can exchange 3000 points for 45 ringgit, while mesra is 3000 points for 30 ringgit....

for mesra card every 1000litres you will get 3k points = RM30
if mesra you spent 1500 litres, you will get 4500 points = RM45
for smiles ron95, every 1500 litres you will get 3k points = RM45
for smiles ron97,, every 1000 litres you will get 3k points = RM45

So from this direct calculation if you use ron95 with petron, the redemption value is pretty much the same

Additional?? 

You pumped 1500 litres of petrol in Petronas, you will get 4500 points (1 litre = 3 points)..then you can redeem RM45

You pumped 1500 litres of petrol in Petron, you will get 3000 points (1 ltre = 2 points)...then you can redeem RM45

Where's the difference??

Unless you use Ron97, then something else