Mainly because its moon phases complication is one of the most accurate currently available and because I find the honey-colored gold case very original, exclusive and attractive. A question for you: you're sure it's possible to buy this model stand-alone? Or rather you have to buy the entire "Homage to F.A. Lange" limited set???
Two personal notes on the two other "contenders". The 5205G Annual Calendar with black dial is a super-amazing timepiece, but - for my personal taste - its dial color scheme is simply... madly wrong. The Santos-Dumont skeleton made me almost crazy the first time I saw it; the second time, I still liked it much; now ... I hate it (sorry!) and I am convinced that its design is not intended to last.
Ciao!