I thought about a WR as well, but, after riding my dads a couple times before making my decision, I realized that his 250F was heavier than my 450F. And I am not exactly a huge person, so I really need a lighter bike. Im pretty sure dirtbike magazine did a weigh in section and found that the WR450 weighs about 30lbs more than the YZ450. Plus, after riding a YZ450 and a WR450 in the same day, I still wanted the YZ even though the WR would probably be more convenient and easier to ride.
Kawi, you just nailed it, CONVENIENCE. If your not in a hurry or enjoy a leisurely pace, the WR will be just right. My 450 weighs approx 20lbs less than my girls WR250. And it feels smaller and nimbler even though its an inch taller at the seat. Its definately thinner.