I am most fortunate to have both these watches, and I will try to address your questions as best I can, in some order.
Maintenance: I would expect both to be decently durable considering they are not 'sport' of hard-usage designs.
Still, either would likely be due some normal (if only preventive) maintenance perhaps every 5 years or so,
with the Patek perhaps requiring occasional service parts due to it's being an automatic. While PP will
presumably be around through any normal lifetime, and will provide suitable parts and service as needed,
for 'factory' service of a Dufour we will have to rely on the gentleman himself, his daughter and
perhaps any assistants. This does include some uncertainty, but I
would venture that as long as there
are well-trained watchmakers, there will be service available for
your Dufour. As to parts fabrication, one hopes not normally necessary, the best I can venture is
that this watch is of a relatively simple design and should rarely have such a need unless damaged or
mishandled. If at such time there is no 'factory' service available, certainly a part can be
fabricated, at a cost probably not disproportionate to the original price of the watch. Still, this
seems to me the extreme end of the service cycle, and personally as an owner, I have no real concerns.
Wearability to me is a tie, these are both virtually the same size, near ultra-thin in proportion, white
metal, simple traditional dial, there is really not much to choose from. The Patek does have that
splendid swing-out back, and terrific screwed lugs, but I think that Dufour's dials (either style) are
really more attractive.
Let's face it, one's exotic mechanical dress watch, whether of the US$13K style or of the US$50K style
can only be relatively 'practical'. Here I suppose there is a positive to the Patek, if it is (G-d)
forbid!) lost or stolen, well you can pick up the phone and purchase another, while at best, and possibly
not forever, you can order your replacement from Mr. Dufour and wait...a long time. So there probably
are situations where one might feel comfortable with the 5053 and prefer to leave the Dufour at home,
but I would think that these would comprise an awfully thin slice of one's life. Perhaps it is best
(if one can afford it) to purchase a 5053 now, and when your Dufour arrives you can decide whether to
keep both or sell the Patek.
Also FWIW, if you are looking for a somewhat less expensive and more 'everyday' mate for a Simplicity,
perhaps you might consider the Chopard L.U.C. watches. I think they are every bit as well-designed and
finished as similar Pateks, certainly more exclusive and (personally) I like the dials and
hands much better. My Chopard is an older yellow gold automatic, but the resemblance to the
guillocheed Simplicity dial is significant and pleasing. Here are my 3: