Are all angitotension receptor blockers the same in terms of side effects? is one more effective then the other? which one has least side effects?

All the same: ARBs, as they are called, have the same side effects as a class and so if you are not tolerant of them, you would need to switch. None have unique side effects. Generally speaking, none is more effective than another in this class. The choice of which to use is often based on your doctor's familiarity and your health plan's formulary.