  We make a critical comparison between ultra-high energy particle collisions
around an extremal Kerr black hole and that around an over-spinning Kerr
singularity, mainly focusing on the issue of the timescale of collisions. We
show that the time required for two massive particles with the proton mass or
two massless particles of GeV energies to collide around the Kerr black hole
with Planck energy is several orders of magnitude longer than the age of the
Universe for astro-physically relevant masses of black holes, whereas time
required in the over-spinning case is of the order of ten million years which
is much shorter than the age of the Universe. Thus from the point of view of
observation of Planck scale collisions, the over-spinning Kerr geometry,
subject to their occurrence, has distinct advantage over their black hole
counterparts.
