The issue is the rehaut. The 1B rehaut isn't as deep as the genuine. And so even though the 1B has alot of the details right, the 1A is actually the better watch to use as a base for modding. But, the 1A requires alot of work. It'll need a new dial, new date wheel overlay, new date magnifier (a slightly weaker one), crown guard work on both the inside and outsides, and a hollow midlink bracelet. All this is in addition to the usual suspects: gen crown and tube, gen insert, and dial and hands relume.
So, all said and done, you're looking at alot of work and money to get the 1A to where it needs to be. I see the 1B as being inferior because you just can't fix the shallow rehaut and that's an important, eye-catching detail.
My $0.02.