I don't think hydrothermal vents started life.
Here are some reasons:

1. For life to start it needs a consistent heat cycle
with enough variety to allow for variant results.
Hydrothermal vents are somewhat methodical, but
they would not have lasted the millions of years
necessary to form all the stages leading to life -
at least not in the same consistent way that the
sun could and did.

2. It is probable that the steam that condensed into
the first rains, and began the oceans - also cleared
the oppressive atmosphere enough to let the sun/uv
shine on to earth for the first time. This window
of opportunity had everything needed for life -
near 100C temps, sun/uv shining and new oceans.

3. The ability of photosynthesis is in some of our
very earliest fossil evidence. It suggests an early
connection with the sun/uv heat cycle. It's hard
to consider a metabolism built from scratch as
a better way, than a sun induced energy every day.
Why invent the wheel when its shining over head?
It's more logical to see the sun as forcing energy
on chemicals - turning the seas into survivors of
'sun selection'  (then as the sun cooled a shift
to chemical selection to compensate for the loss)

4.  Even if meteors or comets sterilized the earth
during this period - a. they would possibly bring in
monomers (like the Murchison meteor) and b. the
sun would be there to re-start the origin process. 
On the other hand thermal vents would shift, or
cease, or move, or raise up new, etc. - far from
being the necessarry Old Faithfuls needed for the
origin.

5. The genetic code is IMO there because of 
the UV damage on the pyrimidine pairs - thus
separating the two sets of bases and aligning them
with different types of amino acids.
Hydrothermal vents could not do that.

Comment?
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