Hat or Hood

A seperate hat in warmer rainy conditions might offer an advantage but for most conditions I'm in, the full neck protection of a hood is desired, in wind, rain or snow. A good shell hood opening can be adapted to varying conditions and a hood is typically lighter than a hat offering anything close to the hoods pro. Wearing a baseball cap under the hood can provide additional protection in wet weather—the brim extending to help prevent rain from dripping onto your face, particularly if your shell's hood doesn't have a pronounced beak.

The only brimmed hat I wear for backpacking is a very light baseball style cap for sun pro, other's prefer the full brim of a Tilly-style hat for the same purpose.

Over the years that have been a number of hats with a waterproof shell based on a Jim Whittaker design. They have a waterproof shell and earflaps that fasten below the chin and often are lined in fleece. GoLite produced one, REI had the Squall then the Winter hat.

The Columbia Kazoo hat is a current example.

My poncho hood is small enough that I wear the hat over the hood.

Both! A billed hat worn under the hood keeps rain off my glasses much better than the hood, but the hood protects the rest of the head and neck better.

I just picked up an OR Seattle Sombrero – it was nothing about weight or better rain protection (although it is good) but all about not losing some of the sense of hearing while I walk in the wilderness.

In the heat of summer, I really don't enjoy wearing rainjacket hoods. They get hot and my glasses still get wet. I'm normally a baseball cap wearer, but I think I'm making the switch to a Tilley for this summer.
In the winter, I don't really care for hoods either. They kill your peripheral vision. Then it's a stocking cap.

I generally have two hats that I take with me on trips.

For cold/wet conditions I will go with an REI WP/B baseball cap. I believe it uses their proprietary membrane, which isn't really that breathable. I couple it with the hood on my Integral Designs Thru-Hiker jacket with great success. In cases where the rain is just a sprinkle I prefer to have my neck area open for venting.

For warm/wet or hot/sunny trips I usually go with a cotton(gasp!) hat with a full brim (sort of a boonie hat witha slightly shorter brim). It gives me a lot of sun protection, and I like the ability to soak it in water for evaporative cooling as I hike. In moderate summertime rain I don't mind my head feeling wet as long as it is not dripping in my eyes or running down my neck. Despite being cotton it works fine for transferring the moisture to the edges of the brim where it drips harmlessly onto the outside of my rain shell.

You got to the essential points. A hood is better in really stinky conditions– if it's blowing hard and raining and cold– the kind of conditions you should be home or wished you were :)

Until it gets that bad, a separate hat is nice. You don't need to wear a jacket to use a hat and it's eaiser to live with in gentle rain and light wind. When it is just plain COLD, I like a fleece beanie that will cover my ears. Beanies and hoods go togther nice. A baseball cap can "cure" a poorly designed hood sometimes and helps keep the rain off your face.