Everybody will tell you that you have to keep the Lange, or to stay with both of them, BUT:
The Goldpfeil is a magic watch, when the 1815 Chrono is only a wise and beautiful watch.
The Goldfeil is a crazy watch, on,e of those who made me dream about watches, Independant watches.
The Goldpfeil is a kick in the ... to those who always say ' Hey, you can't read the Time " when I much prefer " hey what a nice touch of poetry ".
Think different, be a rebel, sell the Lange.
After all, you are already a rebel, since you bought this watch.
Best,
Nicolas.