I think it would be tough to generalize about kung fu, as there is more variation among places calling their art that than any I know of. The two kung fu places I have had the most familiarity with were far more injurious than Aikido.
One had full-contact sparring with minimal protection in which cuts, broken noses and concussions were common. Both emphasized practices which I considered physiologically extreme and biomechanically highly risky. At one place, the guy tried to rush everyone into the ability to drop quickly into the splits, along with many other extreme feats. At the other, they did ascetic practices that seemed crazy to me - like beating one's hands on sandbags and rocks for long periods, until they were bruised and swollen, then reducing the swelling with some kind of chinese balm... all in the name of toughening them up for some kind of 'iron hand' technique.
In general, I'm suspicious of practices that go by the name of 'kung fu' as the connections to the real traditions seem very tenuous, and I've seen more bizarre practices followed dogmatically. Hopefully, the places I've encountered aren't all that representative.