After one month with both headphones, I definitely think that the good one is the Focal Spirit Classic.
It is sad that it hasn't had its own appreciation thread because I think it is the closed headphone that I have listened to that is more similar to the HD650. And that is an endless question in head-fi.
The FSP is good but its low quality construction and bad materials make it unreliable in regards to its durability. Sonically, it is very neutral (and that is good) but it is also less musical, with less body. If you are looking for a truly neutral headphone for monitoring then it is for you (if you don't mind its durability). But if you want a more enjoyable sound, without loosing that neutrality, then the FSC is a better option (with much better build quality and better looks).
So, are you saying that the FSC has different construction than the FSP? I have seen the FSC a couple of times in shows and to me they look exactly the same materials just different color.