I have been running Redline and Syn 3 in my motor since my bike was new, it now has 31k on it for miles. I tried Amsoil once and the top end was very noisy. I have been noticing allot more top end noise in my engine, with Redline being the last oil that I put in there. I know that some noise is normal, but it has been getting excessive. I picked up some Mobil One V Twin 20/50 oil and Filter at my local Auto Zone and changed it. I finally got to put some miles on my bike yesterday, and the top end is quiet, even with 90+ degree temps here in NE Ohio. It says it can be run in the Transmission and Primary, so I'm going to put it in there too and see what happens.

 

I used Amsoil in metrics with great results, been using the Mobil V-Twin in all holes in the Harleys and a Russian Ural (old BMW airhead design) and it's working fine for me. Amsoil is great for friction protection, but has been noted for more noise in some applications where it doesn't seem to have the cushioning effect of some other oils. My brother put Amsoil in the motor, trans, and rear end of an '81 Turbo Capri, and got a noticeable howl out of the rear end, had to go back to the original lube. I've used it in numerous cars and bikes, and got a noticeable increase in gas mileage in most of them. Two strokes pick up some power with it in the gas mix, too. Despite some oils having different noise levels in Harleys, I'm sure they all protect better than the old straight 50 weight guys used to use in the shovel and earlier days.

 

Pick a quality affordable 20/50 Vtwin SYN and stick with it you will be fine. Yes the SYN is thinner and you will notice some top end noise. Meaningless. M1 is a fine oil and buy it when they have rebates get it for about $9.50 a quart and then get a rebate back.
Not a darn thing wrong with running it in 3 holes.