I recently switched to Amsoil 15W-60 Synthetic V-Twin Motorcycle Oil. It is 100% compliant with Polaris Indian TS-111 oil specifications.
While I honestly did not expect any noticeable difference, I am now sensing that the typical lifter/rocker-arm noise may be a little quieter, starting cold my TS111 seems to turnover easier, and the clutch and shifting seem to operate smoother and easier. Honestly, it may all be in my head, or just a result of having put new oil in my Chieftain. Regardless, I am happy with the results, And for several technical reasons I feel much better about having a 15W-60 fully synthetic oil in my Chieftain, which to me makes it worth the extra cost.
Please be aware that there are almost as many very strong opposing opinions about which motorcycle oil is best as there are different motorcycle oils.
I personally prefer to use an oil that meets the manufacture's specification and one that has the thinnest cold viscosity and thickest hot viscosity available. Plus I believe that synthetic is better because it leaves more lubrication on the internal engine parts when the bike has been sitting unused and that reduces friction and wear.
Again, just another personal opinion.