The stock is better treated (as a general rule) at the high-end rodeos. The bucking stock is valuable and well-maintained, and thus treated humanely. There's nothing inherently cruel with bucking out horses and bulls (though some of the bull-riders' spurs, if you look, are rather sharp even for a bull's thick hide).
At the low-end rodeos, there is far less regulation, and far greater instances of cruelty and abuse. Bucking stock is not nearly so well taken care of.
Barrel racers are, well, barrel racers. We've hashed and rehashed that issue in many threads. Some are good and some are bad. Most, despite rough treatment, care about their horses' welfare and don't actually intend to be rough/abusive, and barrel racing is absolutely no different than any other horse sport.
However, any way you look at it, the roping and bulldogging events are cruel. They do NOT simulate actual work on the range in the good ol' cowboy heritage days, when the goal was not speed but efficient, stress-free, easy work on the cattle. Jerking a young calf to the ground from a dead run is appalling, and even at some of the bigger pro rodeos, you will see very rough handling of the horned stock (out of view of the spectators, of course). Bulldogging isn't a whole lot better, and it's got to be extremely stressful for the steer. The same thing with team roping. The way those cattle are "trained" to run isn't exactly humane, either....
At some of the real, good ranch rodeos, they practice a style of roping that is far more realistic for a practical working environment, and this shows a far more useful (if less flashy/impressive) skill as well as being far kinder to the cattle.