Well,
I have used both in patrol engine, By rating goes to shell more suitable and durable for my car.
Exactly it gives you around 6700 km (shell synthetic)
5600 km ( havoline)
If you wish to buy a cheap oil go for honda oil it costs you 740/- only bu the grade is 10W-40W which maynt be suitable for your car.
Consult your cars manual before using or changing the oil.
the minimum 10W-40W is for winter or cold enviroment, whereas the other one is for hot. as i have used both of them i only recommend 10 W-40W , my car is 18 yrs old suzuki swift w/o CNG. and it gives best performance over the singapore packed Shell over havoline.
the choice is yours..
To use cheap oil reduces the life of your car. keep this in your mind.
if you still wish to spend more money try and ask shell dealer to provide you fully synthetic oil it will last upto 10,000kms.