Dipoles: Gives E-field parallel to the dipoles axis
Loops: Give E-field normal to the loop axis
Folded dipoles: same as dipoles but have a higher input impedance (4 times for a regular folded dipole)
you are right concerning their usage, but I think this is because the coupling between the elements is probably higher in the loops and you do not the 300 ohms resonance impedance provided by folded dipoles.