SCHWEINHUND,
From My experience, I have both Windsor & Newton & some Abtl. 502 Oils some are th same Colors & I can tell ya that th MIG Oils seem to be a finer ground Pigment. I've done a wash before on a Panzer & I used th Abtl Shadow Brown & Windsor & Newton's Raw Umber .... It seemed th Abtl flowed better , stayed together & didn't "float" in th Turpenoid.
Plus Abtl has some Specialized colors , not that you could get th same from Windsor , but The Abtl are geared toward th Armor modeler & there's no guess work on th Colors .
I really didn't think there was much of a difference until I used th Abtl Oils !! I really picked up on th Difference ... like I mentioned .. It just flowed better !!
The MIG stuff might be a tad bit X-tra $$ .. but they will still last forever !!