17. Are all starters the same?

No. I think starters are different, a good starter should be
treasured.  Fortunately, the very valuable work of Ed Wood makes it
most simple to prove.  All you have to do is to try the Russian or
another "fast" starter from Sourdough International vs a slow starter
from them.  The behavior of these starters is very very different
with respect to rate of leavening, and ultimate levels of acidity
produced and anybody willing to spend a few $$ can verify this.  I
also think that starters are discernibly different with respect to
flavor.  In fact the classical San Francisco sourdough does have a
signature flavor that no other sourdough I have tasted resembles (I
do not have the SI San Francisco culture so do not know how their
version of it behaves with respect to the signature flavor).

I am also skeptical of grape based starters, etc.  I know Nancy
Silverton and other celebrated bakers advocate this but I can see no
logic in it.  Grapes indeed have yeast and lactobacilli on them.  The
problem is these particular varieties of yeast and lactobacilli have
never been recovered in any sourdough starter that has been examined
from any place in the world.  These organisms are undoubtedly
specific to grapes as certain other lactobacilli are specific to
yogurt.  There are hundreds of strains of yeasts and equally large
numbers of lactobacilli. These organisms develop niches where they
thrive.  To transplant an organism from one natural environment to
another is not a formula for success.  It is like taking a polar bear
and putting it in the desert.  There are hundreds of cheeses made
based on very small differences in starter cultures and processing.
These people are undoubtedly celebrated bakers but to them a yeast is
yeast and a yeast on a grape is a "wild yeast" and they have no
understanding of any of the nuances.  I do not claim to know what
exactly is resident in their starters and whether any organisms they
introduce from the grape actually survive and are viable over time
(years as opposed to weeks).

-Roland