I owned both! Stock for Stock, The CRF250X is more powerful than the WR250X/R (I own the WR250X). It has a more power everywhere, but its probably due to the WR250X emissions, and exhaust, and mapping, etc. ...BUT... I Love the WR250X MORE than the CRF250X for a few reasons...
1) Wider Transmission Ratio, PERFECT for street riding!, Infact, drop a tooth in the front! Great for on or off road! and plenty of speed
2) Less maintenance, less valve adjusting, more riding
3) Better Brakes (at least the X model had nice wave rotors, and a huge front caliper, R model does not have the oversized rotor or caliper)
4) Six Speed Transmission (CRF only has 5)
5) Fuel Injection! Runs perfect in Cold or Hot weather, starts right up everytime!
CRF250X advantages
1) Separate transmission and engine oil
2) More power stock
With some mods on the WR250X/R (drop a tooth in front, fuel programmer, new exhaust) you can have a nice powered machine which is great for street and off road, overall the WR250X/R is a superior machine for on/off road