[ Ref. http://www.youtube.com/watch?v=jK-xoOL1ShQ
  Duo-Art
 [ and  http://www.youtube.com/watch?v=QybqhcPRHBI
  Ampico

Perhaps the most significant aspect of Ralph Nielsen's posting is
the fact that he has featured these two entirely different systems
in nicely restored playing condition.  The rolls have huge
differences of interpretive nature, yet each renders a pleasing
musical performance.

Other contributors have mentioned comparing rolls more similar.
The "Trio" rolls (Ampico, Duo-Art, and Welte formats of the same
performance) come to mind.  Even then. some astute collectors have
noticed slight differences in how those rolls are coded for their
respective systems.

Pending a more complete regulation and adjusting, I might attempt such
a comparison.  I have one or two of the trio rolls.  I can play Ampico
and Duo-Art rolls on two 7' pianos which will somewhat level the
playing field of instrument size.  (My pedal-electric Steinway 7'6"
is still a work in progress.)  However, I don't think the differences
will be discernible once the videos and recordings are made.

In any event, congratulations are in order to Ralph Nielsen for jobs
well done, and for his YouTube postings.

Bob Taylor
Missouri