Do pilots on the 75/76 choose domestic/international flying just by bidding?

They fly completely differently. The 757-200 is indeed a hotrod. A well designed wing and lots of power gives it incredible performance. It's very heavy on the controls but feels natural and doesn't really have any bad habits. The 757-300 not so much. It lumbers around the sky, doesn't climb very well, and lands like a lawn dart. Similar problem to most overstretched airframes: not enough wing for the added weight and there's only so much extra thrust you can squeeze out of an engine variant before it needs a complete redesign too. The 767 is very gentlemanly. Imagine someone took the power steering from your grandpa's Cadillac and turned it up to it's max pressure. You fly it with two fingers and it's very light on the controls, especially in roll thanks to the inboard ailerons. You fly it with two fingers. When coming off a couple of months of 757 flying it's very easy to over control it for the first couple of minutes. You also have to be careful on rotation because it nose comes up quick, unlike a 757 where you need to yank it off and if you carry that technique over to the 767 you run a pretty good risk of hitting the tail. Performance is also very good and it's fairly forgiving but you need to be careful when heavy because the flap limit speeds and minimum maneuvering speeds are very close. You have a pretty narrow window when retracting them after takeoff between overspeeding something and getting the stick shaker. For that reason at my company the 767-300 is the fleet with the most stick shaker events. It doesn't help that we don't have speedtapes and need to rely on old fashioned bugs on the analog airspeed indicator and flap speed limits on a placard to keep a mental picture of where we are. I also find it harder to land than a 757. The forward gear tilt makes it very unforgiving of even the slightest side loading. You might be set up for a greaser but if you're just a little bit off it will shake the whole airplane as the bogeys settle. It also comes out of the sky when you pull the power so you have to be much slower in going to idle, especially if you have GE engines which spool down almost instantly. In a 757 you can wipe the power at 30ft and still be ok if you're on speed, do that in the 767 and you're dropping oxygen masks at the very least if you're lucky enough to not need a hard landing inspection.