If you are going to keep a watch forever, then of course it makes absolutely no difference. Many of us are flippers however. Todays grail becomes next weeks sale. And nobody knows for certain how well we will like any given watch over time as we live with it for a year or two.
So lets consider the purchase of a reasonably expensive watch (value retention of a $500 watch is pretty meaningless). Do you still buy a $5000+++ watch knowing that the brand in question does not hold value well?
Of course, if value retention were the only factor in better watches, we would all buy only Rolex and Patek which can usually be resold for 90%+ of their original MSRP (as long as you choose the model with respect to resalability, there are some Rolexes and Pateks that are notoriously unpopular and difficult to sell). But most other brands just don't hold up that well and often sell for 50% MSRP used. These brands need to be purchased new with at least 20-25% off MSRP or you will really get burnt. Rolex and Patek new discounts are usually minimal at best.
There are some watches that are extaordinarily difficult to sell on the used market (I won't name names) and you will likely take even more than a 50% haircut if you can get it sold at all. Are you brave enough to buy a watch like this?
So how important is value retention of a particular watch in your buying decision?