A couple of things consider also: the two piece nylon strap will sit higher on the wrist because of the extra layer of fabric that sits under the case-back. And, if you have a smallish wrist (like mine) ,the nylon or NATO straps tend to flare out slightly from the spring bars, thus making the whole thing look a little bulkier on the wrist than it ought to be. That's why some people prefer the single strap that goes under the watch. It sits lower and makes it easier to adjust the watch so that the buckle sits right across the middle of the underside of the wrist. The double strap versions tend to be safer if one of the spring bars comes off. The watch will just hang from your wrist because it's still attached at the other side. Also, if you're worried about the integrity of the spring bars, you may want to get some heavy-duty ones. I have noticed that the bars supplied by Breitling for their watches tend to be thicker than most.
I have seen some pics of the black Seamaster on nylon straps and it is a nice looking combination. Gives the watch a real "SAS guy on his day off" kinda vibe.
Regarding durability, I have read that these straps can be thrown into a washing machine when they get dirty and they come out looking like new.
I like these straps. When the day comes that I can afford a pre 1984 Rolex Submariner 5513, the first thing I'm gonna do is put a NATO strap on it to de-yuppify the watch a little.
But for you, GMTtraveler, the real problem is going to be finding the right shade of blue to match the color of the dial. And believe me, once you go down that road, you're in a world of hurt.
I hope this helps.
Good luck.
teeritz
