Very good info from all on the Marlins. What is lesser quality from Walmart aside from wood ? I see these 336W's fer sale but retain high price due to jm stamp.
Any help, suggestions ?
The general formula for a 'W' model is:
Cheaper wood (typically Birch).
Cheaper sights.
Lower grade fit and finish.
No sling swivels/studs.
The parts used, standards held, and quantity produced varied greatly over the years. But most - not all, but most - of the more recent examples (roughly 1998 to 2008) used aluminum sights instead of steel; really cheap, soft birch stocks with minimal machine time (utilitarian styling); a cheap, easily damaged finish on the wood; and more of a wire-wheel (rougher) finish on the metal than the '220 grit' type of finish on other 336s.
My own biggest complaint about the more recent 336Ws (again, roughly 1998-2008) is that the Birch stocks were very poorly fitted to the receivers around the upper and lower tangs. That being where all of the recoil gets concentrated, can be a problem. They are more prone to splitting at the tang than other 336 stocks, and repairs seem to be more difficult to hide, due to the softer wood used.
That being said...
I actually prefer the cheap, aluminum Williams rear sight that Marlin used (on and off) on the 336Ws in the '80s, '90s, and early 2000s. For me, it gives a better sight picture than the standard steel leaf. It is also secured in the rear sight dovetail by a set screw, so it can't be bumped out of alignment like the standard sight. I don't really care for the aluminum front sight, but they're easily replaced with aftermarket blades and bases.
And, slightly lower finish quality, or not, the receivers are machined exactly the same, are made of the same steel, and are heat-treated to be just as strong as any other 336.
Right now, I am building a custom .444 Marlin with a 336W receiver (2002 production). I have no reservations about longevity or reliability from extra 'abuse' that the more powerful cartridge will give the action.
I never really liked that 2002 336W as a .30-30, but I also never had any doubts that it would continue to function as intended for a long time to come....
(Until I tore it apart and put it on steroids...

)