Bullet shape will be better.

Thanks Sohail sir. Actually the tank is not be a pressurized one, rather a fuel storage tank. Generally, I have noticed that bullets are used for pressurized storages. What u say?

Hydrostatic pressure of oil will subject a tensile stress at corner joints. To minimize the stress concentration at sharp corners is always preferred. Also, in case of likely lateral bearing loading caused by liquefaction of soil outside the tank will have minimum stress loading in case of bullet shape.

Thank you sir. Also stress concentration causes accelerated corrosion. But what I am concerned about is that whether the bulging part of the bullet,unlike cylinder that has flat sides, would bear the vertical load of the soil?

use of radial stiffeners (just like cycle spokes with thick rim) inside the tank at appropriate interval will take care of the soil bearing load.