I purchased several winter cycling hats / headwarmers this winter to try to find something that would fit under a helmet nicely and also keep my ears and head warm. The Hincapie Alpe Brim Hat ended up in second place behind the Rapha Winter Hat. Overall if I had to recommend just one hat, it would be the Rapha Hat, it is only a few dollars more (retail prices) and is much more versatile and I have ended up wearing it the most.
Both hats have traditional Belgian styling with a brim and ear-band. Rapha's brim is a little larger in every dimension and is also a little stiffer. It keeps its shape better, but can obscure your vision a little more than desired depending on how deep your drops are. On the tops/hoods both brims will block moisture and glare equally well. The Rapha hat has longer earflaps and they cover my entire ear, keeping them nice and warm into the mid 30s. The Hincapie hat in L/XL leaves my earlobes exposed (but I do have a large head - size Largo Giro helmet)
The Hincapie hat is constructed from a softshell material that seems to fend off rain pretty well, but is very slow to dry out from perspiration (it will usually still be slightly damp the next day, the Rapha won't).
-Warmest hat I've found that still fits under a helmet well
-Full coverage ear flaps
-Comfortable from mid 30s to 50s
-Better water resistance
-Less bulky / but also less warm
-Can fold up the ear flaps with a helmet on (the Rapha ear band is too thick to do this with a helmet)
-Comfortable from low/mid 40s to mid/high 50s
Bottom line - unless it is raining or warmer, I will choose the Rapha, but this is a good hat to have in your arsenal.