Hello Amanico, again an interesting post and comparison.
All the points in the thread are pertinent for the purpose of the persons point of view except the movement in the Montblanc being better, it being SS and so on. The size of the MB is not an issue for many, I have a 6.75 inch wrist and the 1858 fits me well, in fact for the longest time I thought it was 42mm until a friend teased me for saying that. I also believe the dial on the Montblanc is prettier with the starbursts effect and the chrono sub dials aligning. And let’s not forget the Montblanc 1815 Minervas are limited to 100 each SS, RG or Bronze, Patek is not a limited edition.
I know talking pricing and discounts is discouraged so Mods please delete if you think I’m out of line here however I want to clear up the pricing debate. The 5172G is $73,710 USD, not sure if it will be discounted but the Montblanc is discounted at least 20%-25% (if you ask) with the US retail at $25K for the steel and $30K for the rose gold.
So to be apples for apples let’s use the RG Montblanc to the WG Patek. The RG Montblanc would come at $22,500 with a 25% discount, If the Patek were discounted 10% (only a guess) it would come out $66,339 so the delta is closer to 3x less for the MB in previous metal.
For my money the Montblanc is the clear winner in this comparison and I will add that I believe if you buy a Montblanc at the discounts mentioned above the value will hold consistent with only 100 of each being made.
For a little fun I added two pictures off the blogspot.com site of my 1858 Bronzo with the rose gold added to the movement...Jim