The rm250 has been number one on just about every mx shootout since 2004 but everyone has their own opinion. I wouldn't go for a tm, gas gas or husky because parts are dearer and not readily available like the jap bikes. And they wont hold there value as nobody wants them.
I suggest you have a look at a second hand TM or GASGAS before passing comment on resale values,
eg: on resale values according to "THE RED BOOK"
:2006 TM mx125 $2200 less than new price last year
:2006 GAS-GAS mc125 $2295 than new price last year
:2006 RM125 $2890 less than new price last year
You do the math...