Check out what international flight crews use: mostly car-bumper-material hard cases. The reason is, there is a good chance your bag will end up at the bottom of the container, with everyone else's piled on top. Also, soft cases, especially those with straps, are easily caught on pointy bits along the luggage path, and rip. I have seen too many soft cases come off conveyors in shreds to count.
A good argument for the standard models from well-known brands is that Myers regularly have them on special, and if they are damaged, they can be fixed around the world. (NB: if your luggage arrives damaged, go to the airport's luggage section and ask them for a voucher for repair. The airlines' insurance covers this, even if this is not advertised for obvious reasons.)
Samsonite is the champ here, although I personally prefer my 25-year-old Delsey that has been around the world a few times: flush name-tag window (external tags get ripped off), all handles spring loaded to lie flat (unlike my wife's Samsonite that had the flapping solid metal handle bashed into a hook shape) and has both key and combination locks. I too find the two-wheelers easier to maneuvre: for example, they can be reversed at speed into tight lifts.
However, security is overrated. If airport thieves want to open a bag, they will: they have the time and experience. So the lock is mainly there to prevent the case from spontaneously bursting open. Valuables belong in your carry-on, or should stay at home.
In my experience, the best carry-on is as big as the legal limit. This way it may be enough for shorter trips, and you can save the extra time and hassle of checked luggage. I used to carry a soft pilot bag from KMart ($20, and very light), but with advancing age have opted for a wheeled bag instead. An abundance of nooks and crannies and pockets and sections is best, to facilitate packing. Carry-ons are more of a personal preference and cool rational logic is less applicable than with checked bags.