I've owned a Powerbook (matte 17"), Macbook, and a Macbook Pro Glossy. I've also extensively used our Macbook Pro Matte at work, outdoors.
All laptops suck in the sun. It's not just laptops either -- CRT TV's, Plasmas, fluorescent signs, everything becomes hard to read with so much ambient light.
It's true that a glossy will reflect more in the sunlight, but it is by far the better choice. The matte finish diffuses so much light that it's hard to read at any angle. I have to turn my matte display to full to barely see anything, and then I end up trying to shade the screen with a jacket or under a tree, and move up 3-4" away to see anything. The glossy screen just has glare galore but if you can see past the glare (which usually jsut takes some tilting of the screen) there's a decent viewing underneath.