The s3 is a compound and the s17 is a polish. You wouldn't necessarily have to refine the finish if you used the s17 but if you used the s3 you would then need to use s17 or another polish to refine that as it's very abrasive.
S3 gold is great but as has been said it will definitely need refining, I corrected my car with it recently and was left with buffer trails until I refined it.
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