Personally ,I do not argue with the guys that make the stuff! Almost (make that) ANY powder can and will give you different results from different lots.
I am of the same mind as jhalcott. I spoke with Hodgdon/Winchester, and H110 and W296 are "...the same powder, always have been..." and "...you can use W296 load data for H110".
That being said, lot to lot variations will also occur. You should always start conservative and work up..etc., etc., etc. If you have loads developed for H110 and want to use W296 instead, you might want to work up conservatively again, just to be on the safe side. It wouldn't hurt, while others may think it a waste of time. You may find a different accuracy or power curve with the different brand that works better (or worse). Your choice.
My interest in the interchangeability between powders came from trying to locate powder in my town. Load data is just that, data. Your loads in your gun are something else - they can hurt you if not done right. Ultimately the responsibility rests with the loader and user of the ammo.