  Magnetic Penrose process (MPP) could be highly efficient (efficiency can even
exceed $100\%$) for extracting the energy from a Kerr black hole, if it is
immersed in a mG order magnetic field. Considering the exact solution of the
magnetized Kerr spacetime, here we derive the exact expression of efficiency
($\eta_{\rm MPP}$) for MPP, which is valid for both the Kerr black hole (BH) as
well as Kerr superspinar (SS), and also from the weak magnetic field to an
ultra-strong magnetic field $(B)$ which can even distort the original Kerr
geometry. We show that although the value of $\eta_{\rm MPP}$ increases upto a
certain value of ultra-strong magnetic field ($B_p$), it decreases to zero for
$B > B_p$, in case of the Kerr BHs. On the other hand, $\eta_{\rm MPP}$ shows
the opposite behavior in case of the Kerr SSs. One intriguing feature that
emerges is, $\eta_{\rm MPP}$ acquires the maximum value for the Kerr parameter
$a_* \approx 0.786$ (unlike $a_*=1$ for the ordinary PP), decreases for $0.786
< a_* \leq 1$. This indicates that the BH starts to expel the effect of
magnetic field for $a_* > 0.786$, and is fully expelled from the extremal Kerr
BH due to the gravitational Meissner effect. As a special case of MPP, we also
study the ordinary Penrose process (PP) for magnetized Kerr spacetime. We show
that MPP for Kerr BHs, Kerr SSs and ordinary PP for Kerr SSs can be
superefficient for the astrophysical applications to powering engines in the
high-energy sources like active galactic nuclei and quasars, in the weak
magnetic fields. Our strong magnetic field result of MPP could be important to
the primordial BHs in the early Universe immersed in the primordial magnetic
fields, and to the transmuted BHs which are formed by collapsing and/or by
merging of the magnetized progenitors. It is almost impossible to extract the
energy from a BH (SS) through MPP (PP) in the ultra-strong magnetic fields.
