I saw your bike on CL
I saw your trusty 950 on Craigslist and wondered what would be next for ya. I've not ridden either of the bikes your looking at but I can tell you my 2003 yamaha is ultra reliable, and the market is flush with them making them cheap to pick up. Looks like I'll be selling my plated wr250f to get a 2007 yz250f. The YZ is so much lighter than the WR, I don't need a 450 though. I've read the fuel injected YZ450 can be electronicly tuned for smooth power or the big hit of a stick of dynamite.
As other folks pointed out both bikes are reported to be great.