I know the forum mold has taken over thread, but for the OP, different oils will have different effects on the clutch. Not so much negative or positive, but a different feel. Personally synthetic makes the bike feel like the rear tire is spinning on take off because the oil is a little slipperier and requires more clutch pressure to grip. Once I let the clutch all the way out, it's fine, but I just don't like the feel during takeoff. I've heard others say the same thing on other bikes. Mineral oil has a more consistent feel on the clutch, at least to me, so I rather use it for that one reason.
Most folks don't consider this a positive marketing point for Harleys, but the clutch area (Primary) on Harleys is seperated from the Crankcase. This allows using two different oils if desired. Synthetic in the crankcase, nonsynthetic for the clutch. That allows using the advantages of both oils.
Beary