I have experience with both. Am currently on a Gas Gas 250. My previous Gas Gas was a 200. I've had a 125WR Husky, and a old 400WR Husky. Also, a riding companion has a WR 250. I do like both bikes. I prefer the power delivery of the Gas Gas, and overall the chassis on the Gasser gets a narrow nod. Can't point out to you why, I'm just more confident on it. As far as parts. The Gas Gas is so much better supported nation wide, as far as I'm concerned, and the parts are less expensive, and very quick to get. I never had problems getting Husky parts, but it wasn't always quick, or cheap.
I will tell you this though, all things being equal, I pick the Husky. My Husky's, and my friends Husky's, are the toughest, most reliable, solid, tight motorcycles, for the most miles of any bike I've ever owned, including a '00 XR 250.
Total reliability-Husky
Total joy of owning experience (support is important)-Gas Gas