The simple fact that HD delivers MC's with Syn3 installed tells you it aint great oil, if it was the motor would never break in. Any good synthetic stops wear, translated to never seats the rings in a new motor.
My choices from many years of race motor (auto) experience;
Red Line
Amsoil
Mobile 1
in that order.
The trick in race motors is to get the rings seated quickly without damaging the cam. Then get it on Synthetic to keep it alive for a long hard run. Ideally you would run 20w, non detergent to seat the rings, but synthetic to break in the cam. Since you cant do that you compromise on a break in oil. Then switch.
We have even put an old cam in the motor to seat the rings, broke in the cam in another motor with synthetic, then switched parts & oil. Works, but is a lot of work even on motor stands that allow you to run the motors.
I switched my 06 FLHTCUSE to Red Line 20-60 at 2500 miles, put Red Line MTL in the Primary & Red Line Heavy Shock Proof in the Trans.
These are actually the recommendations from Red Line, (I have a friend there). If you are in cooler areas where the outside temp's don't get to 100+ use 20-50 instead fo 20-60.
Just my 2cents