How often do you intend to shoot arrows? Air bolts that must have their fletching twisted to go in the barrel will eventually need to be re-fletched. That's my understanding anyway. Dedicated arrow launchers, like my pioneer airbow, can in theory can be shot an infinite amount of times.
I don't believe the rattler would work due to how it's magazine cycles and how air bolts are pushed in from the muzzle. But of the ones you listed it's the one I'd want due to semi auto. My current big bore is an aea challenger. Aea doesn't have the best reputation especially on their semi autos, and i had to have a sear made for my challenger out of hardened tool steel because the one it comes with was made of poor material and broke. I seem to recall seeing that newer ones solved that problem. I like it because it has a 6 shot magazine. Might be worth adding as a consideration to research. Hammers had issues when they first came out as well, not sure how reliable they are these days. I never had a western bush pig but used to have a bushbuck. They're ok although I was unlucky with mine and had a power issue that AOA was unable to fix. I can not recall ever seeing anyone with a serious issue with a Texan, though I've never owned one, only because I'm not the biggest fan of their looks and ergonomics or single shot operation. Possibly consider a Seneca or for lotsa dollars, an AAA slayer. Benjamin bulldogs have a pretty good reputation too.
One more thing, it personally think the new m600 airbow was an unnecessary "upgrade" from the original. It uses more air pressure, yet gets fewer shots, and is unregulated unlike the original. ( the original fills to 3000 psi and delivers 8 regulated shots, all at 450 fps, the new one fills to 3600, yet only the first 3 shots are up to 600 fps, and while you can shoot it after that, velocity will start to drop which means the same for your point of impact.) What do you get for this trade off? More powerful arrows when the original already rivaled the world's most powerful crossbows. The originals arrows went 450 FPS which is 168FPE. They will shatter if you miss and hit anything hard, like the ground, 19 times out of 20. I bought a special crossbow velocity rated target to stop the arrows, normal archery targets are insufficient. Its already difficult to pull the original airbow arrows out of my target without a rubber arrow puller and still kinda tough even then, I have to sit on the ground and put my feet against the target to hold it back while i pull the arrow straight out. The newer one will penetrate even deeper and may even require an even more resiliant target i suspect. So me personally, I'd rather try to get an original pioneer airbow than the new more powerful one. I just checked Benjamin's, site, they still sell the original, they just call in the 450, and it's 300 bucks cheaper
