I like a lightweight carbine, and the more weight on the front of the rifle the heavier it feels.
I must admit the M4 barrel looks great, but is there really a big disadvantage to the lightweight barrel?  If the weapon had select fire then the choice would be easy.
But for a rifle fired in the semiauto mode only, does anyone foresee significant problems???
thanks
P.S.
the rifle would be used for plinking at the range, home defense, etc. (not for competition)

thanks again-

If its all close range or you wont go over 2 mags in a single "defense" scenario then the LW will be fine.

If it didn't work, Colt would not have sold tons of 6520's and 6530's.  The lightweight barrel sounds ideal for your needs.  Personally, I find the slightly more muzzle heavy M4 points and tracks better.

I don't see any problem - just advantages.  I prefer my 'lightweight' to my M4.  It handles better IMHO.