Newer 250 Mx Bike Or Yz426f...??

I'm gonna have around $4,000 to get a new bike in about 1-2 months and I wanted to know what you guys think would be better for my type of riding/ situation I'm Set on either a newer(1999+) 250, or a yz426f The bike has to be decently reliable (able to go on rides without worrying)............???

~My Info~
(Hight)-6'1
(Weight)-165lb
(Type of riding)-Dunes, Mx Track, Desert, Rarley trails
(Previous bike)-Slightly Modded rm125

So....What bike would be the best choice??

you guys are soooo much help.....