As a serious collector with 3970 and 3450, how come you need to ask others' opinions?
I think many of the aficiandoes here could not attain the holy grails you own.
Having said that, I would choose a 5050 as the retrogarde complication is not in your current collection now
the most beautiful perp/chrono I have ever seen - the 2499YG in whatever series. That's just my personal opinion.
cheers
fernando

....... in terms of choices. Whatever is available for your picking, i would pick the one which is the most complete, meaning box & paper, and if possible, an un-touch case. with the sharpess lugs, strong hallmarks, unwashed dial.
AT this very moment, your choice is far and wide, but to narrow down the a choice of one, i would put these criterias on the table as consideration.
This would make your hunting game more interesting.