The movement of the 1815 chrono is virtually unparalleled perhaps only rivalled by the Patek 5070. It is basically the Datograph without the date and is extremely good value for money relatively to the Datograph and Patek. However, it is quite a heavy watch which may not suit some people. I had mine for 3 weeks and sold it as the weight really bothered me. I have since opted for the new 1815 up and down, a different proposition altogether but a more wearable watch.
The Lange 1 moonphase is a nice watch if you must have a Lange 1 but if the accuracy of the moonphase is important, please note that the moonphase is accurate to one day every 122 years compared to the 1815 limited edition moonphases (both Emil Lange and the more recent honey gold version) which are accurate to one day every 1,058 years ie 9 times more accurate than the Lange 1 moonphase. Arguably, it would be difficult to tell the difference and if accuracy was that important, then, the Christian Van de Klaaw moonphase watches are among the most accurate.
I love Pateks but Lange's finishing is arguably second to none among the big brands. The 1815 chrono has such a beautiful movement that no one would hold it against you if you wore the watch on its reverse side!
Good luck with your purchase!
Sham