Gary is out of office, but I'll chime in on his behalf. Both are very good tires. The PSS has a bit more grip, and very responsive handling. The S04 has very stable, confidence-inspiring handling, so even though it is slightly behind in lap times on the track, it is very rewarding to drive. You will find people who like both.
If you are reluctant to change sizes, the S04 is an excellent choice.
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