PeterCDE
10167
Well....
G'day,
i´m not sure to understand the approach correctly, but some thoughts:
The Grand Lange 1 with luminous dial (ref. 115.029) is a regular model and not limited, other than they are doing few of them each year. Well, they do few Langes of ANY model, much less than almost all higher brands.
The Lange 1 certainly is an icon for the brand, but in the watch world as well. There are not that many pieces universally regarded a milestone model, which already is a good reason to add a Lange to your collection 
As per "better buy", first of all i´d like to point at our guidelines; we´re not really comfortable to support lengthy "investment strategy and value" discussions.
As usual, both are probably less effective investments than real estate or stock markets. After all, shares don´t need regular service and come without signs of wear
Personally i´d recommend to go with the one that will provide you more pleasure.
Try both and take the one which makes you smile more
The most apparent difference, apart from the very different style, probably will be the size. The Grand Lange 1 measures 41.9mm in diameter, which makes it a *very* substantial piece. The Breguet 7027 is 38mm in diameter and while not small, on the wrist i recall a significant difference towards the Lange.
In any case, you can´t do wrong with a Lange. These are fine watches.
Cheers,
Peter