I believe there is a reason to who prefers Shinn over Kira and vice versa. I believe this might have to do with the order in which people watched the SEED series.

My Hypothesis: People who think Kira > Shinn watched GS then GSD while those who think Shinn > Kira watched GSD first then went back and watched GS.

Edit: Is the poll working? If not...geez...I feel like a n00b.
Questions:
Kira > Shinn; Watched GS prior to GSD
Kira > Shinn; Watched GSD prior to GS
Shinn > Kira; Watched GS prior to GSD
Shinn > Kira; Watched GSD prior to GS

If a mod would be so kind as to fix my n00b mistake if this doesn't work.