I understand, as many others too, your reservations regarding these two watches and the retrograde hand.
But as Oliver is saying: I also do not think that Patek has produced something that does not work reliably.
However the 5159 changes in movement are that no longer one 48 notched (for each month) wheel is used (like in the 5050) but only a 12 month wheel with a satellite wheel with four notches for February.
Although it means more parts I can imagine that smaller wheels are better to control.
Secondly " speaking against" the 5050 is the fact that most are over 20 years old and regarded by Patek as classic collection with an estimated service.
Patek and estimated are words that can frighten a collector .
On the other side the 5050 is much smaller hence more classic, gives the choice between batons and roman numerals.
And if the 5050 would be a bad in performance the market would be flooded with them but it is not.
As the headline is saying: either you "do not care" about the service and reliability and go for classic or you are concerned and go for the modern.
I personally would also go for the gorgeous 5159 R, but also the G version.
Moritz