Let's make an overall ranking of the relations. When seen from a romantically perspective.

1) Duality
2) Identical
3) Mirror
4) Activation
5) Illusionary
6) Semi-Duality
7) Look a like
8) Benefeciairy
9) Comparitive
10) Supervisee
11) Benefactor
12) Contrary
13) Superego
14) Quasi Identical
15) Supervisor
16) Conflict

After reading your opinions, i've edited some. Identical has been described as second best in some socionics journals, but it seems that it's not how it is experienced...