[EM] Advantages of the two-round system vs Schulze method and contingent voting

[Peter Zbornik]

Hello,

an other question I wonder if you could help me with:
For single winner elections we currently use the two round system, which is
equivalent to the Contingent vote providing that the voter does not change
preferences see http://en.wikipedia.org/wiki/Two-round_system and
http://en.wikipedia.org/wiki/Contingent_vote

<http://en.wikipedia.org/wiki/Contingent_vote>According to the table on:
http://en.wikipedia.org/wiki/Schulze_method#Comparison_with_other_preferential_single-winner_election_methods
,
Contingent voting <http://en.wikipedia.org/wiki/Sri_Lankan_contingent_vote> has
no advantage over Schulze method (apart from being a few dimensions simpler
in terms of vote count and understandability for the common person).
Two-round voting (although widely used) is not listed in the table.

The questions are:
1) Does the two-round system satisfy any criteria, which Schulze method
fails, apart from complexity and understandability and the option to change
preferences between election rounds?
2) What criteria does the two-round system satisfy that the Contingent vote
does not satisfy and vice versa?

Best regards
Peter Zborník
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