I tested all four for Trail & Track back in the day.........
CR250RE - needs a rear Ohlins, breaks pistons on exhaust port, with that done..the best.
KX250C2 - good everywhere, the high rear mudguard smacks you in the arse all the time.
RM250E - Best handling & rear suspension, if it had a front disc it'd be a winner.
YZ250L - Z spokes were not reliable, most low rpm power, if it had a front disc it would be a winner.