"What's more likely. A Big Bang where everything starts from a
singularity or M-theory Big Splat (ekpyrotic scenerio) where two higher
dimensional colliding branes produced the matter and energy in our
universe?? "

There are BB theories that do not start out as 'singularities', one of
which was developed by Hawlking.

In any event, the physics we understand today is simply not capable of
describing much about the universe before around 10**-35 seconds and is
completely incapable of describing the universe before 10**-43 seconds.
A lot of strange physics occurs between t=0 and t=10**-35 seconds.

As I understand it, the ekpyrotic scenario evolves into the BB senario
around plank time (10**-43 seconds) but is based upon physics for which
not test has yet been devised to acertain whether these string theories
are a part of physics or part of philosophy.

In addition, the colliding branes only release the energy that is
embodied in our universe, it took until about t=300 seconds for the
first atomic particles to condense out of the fireball. That is; matter
is simply condensed energy, and the BB (by whatever means) was pure
energy until the universed cooled to the point where mater could exist.


The only really strange part is how were the diemnsions of space and
time were released in the BB.

I suspect that when these theories are more developed and more
measurements are performed, that they will either converge or become
different mathematical tools to describe the same set of events.
Thereby, I refrain from picking a winner, but get to watch it all play
out (hopefully).