No offense, but like Aggs said, neither is something that you just decide "well, it looks like fun" and give it a shot with any hope of a positive outcome.
If you want to just try one out, then you might get in contact with your local college or high school rodeo director. They generally have stock for practice and training that is easier to cover than real rodeo stock...and they can give you help about how to stick with them.
I've rode a few bucking horses (didn't want them to buck, but they did) and I've also rode a few steers in my day. Truthfully, I don't want to do either of them again. Just too much risk to getting hurt...especially if the stock level is above a person's capability.
With no experience, the best you're likely looking at is a buckoff right out of the gate...so short you don't even get to enjoy it. The worst is serious injury or death. Rodeo stock isn't something to screw around with just for grins and giggles.