Well, if you're looking for two larger crotes, these are good choices....As far as caging, both can be kept in simple, lockable enclosures outfitted with a hidespot, water bowl and the right temps. The canebrake may require slightly higher humidity, but other than that, they are pretty similar in terms of caging.
As far as size, both of these animals can reach impressive lengths and girths in captivity. While an "average" adult length is somewhere in the 3.5-4 foot range, both of these animals can reach nearly 6 feet, and at this length are truly impressive...In fact, the record length for an atrox is a shade under 7 ft.....
In regards to toxicity, either of these creatures can inflict a nasty, potentially life-threatening bite. Certain populations of canebrakes have powerful neurotoxic components in their venom, making them extremely virulent. Atrox's venom isn't particularly potent (LD50 of about 5mg per kg) but when you consider the enormous yield they can expend in a bite, they are truly a dangerous animal. I'd put the toxicity of horridus above atrox, but atrox has a larger yield, so I guess it's pretty much a wash...Long story made short....Don't get hit by EITHER of 'em!
Temperment....well like everything else it can vary...As a rule, atrox are much more "nervous" than horridus, but this isn't always the case. In my experience, atrox is much more prone to "sounding off" and adopting defensive behaviors than is horridus. However, I have seen quite a few atrox that were relatively laid-back....
Both species are relatively easy to keep and CB examples of both are often voracious feeders on pre-killed rodents. I'd recommend a CB neonate or juvenile to begin with....that way, you can learn about the particular snakes' quirks BEFORE it acquires a large strike range!
In summary, both species can be easy to handle, provided you know what you're doing. Good luck with whichever species you choose...
-Kris