I'll start with the very small complaints. I think Oakley could put a little more design and tech into the core foam of the helmet, like what Smith uses. Second, the sweat band takes getting use to. But then... the sweat band is freaking awesome! It totally works keeping out moisture and aiding with glasses fog. The glasses storage on the back is also sick (don't use while heavy DHn though). The visor on the helmet is the best I've ever had. And last but most important (kidding) It's the most stylist helmet on the market and has a nice low profile look.
My Synthe was 4 years old so figured it was due for replacement. I assume the Spherical technology of the Helios provides a greater level of protection than the Synthe (MIPS only). Overall the Helios has a better finish than the Synthe and operation of the RocLoc is definitely smoother and easier. The Helios uses pad strips in the top which I don't think provide quite the ventilation of the plastic "basket" the Synthe uses. My one complaint about both helmets is that the chin strap buckle adjustment tends to creep loose and require tightening every few days.
Top notch "barely there" sunglasses that work well in any condition. It is incredibly light weight, sits on the nose and temple softly, has no frame to obstruct the view....so practically you can forget that you are wearing anything. Except that you see better in rain, shine and shade. I have been abusing my first pair and still works like new. No matter how aero the position, when I look up I never have to look OVER the lens, always through, so no wind and bugs hit my eyes either, which has been an issue with smaller lenses.