If the bucking is meant to get you off, then I'd much rather go with a rear. I've been bucked off bronco times several times, and while I was lucky not to have broken anything, I'd much rather sit a rear. Hear's why:
When horses rear, in general, its not to unseat you.. The easiest way to do that is to buck. Rearing comes from a) a bad habit, b) spooking, c) not understanding what you want and responding to a strong bit.
If your horse has a soft mouth, and you are yanking and pulling on the bit, eventually you'll get them to rear. Some horses rear when they spook, though I've personally never experienced it. I've ridden bad habit rears and not understanding rears. Here's the deal closer: Rearing (especially with a rider) requires a lot of athleticism, to go fully verticle is almost impossible for most horses, except those extremely well balanced and well muscled.. Generally riders who lean forward will stop a rear before it gets much higher because they mess up the horse's flow by moving.
Bucking however is more of the horse "throwing a fit" and true bucking meant to get you off: will get you off almost every time, unless you catch it right away. Any horse can throw a fit, and even an untoned horse can be a very strong bucker if you p*ss it off.
Not only does rearing require muscling and talent, unless the horse truly is spooking, it requires a lot of confidence. Its something the horse either does at play in the pasture or in his stall out of boredom, etc. In general a horse won't rear under saddle out of nowhere, the habit is picked up somewhere else and translated under saddle with some sort of stress or trying to distract the rider from working.
My filly used to rear under saddle, it became almost guaranteed every time we rode. She also would get on her hind feet in her stall and look over the stall wall at the other horses. She would balance herself on her hind feet for quite a few minutes, she looked like a Lab really. Yet it was her bucks that threw me off and left me bruised for a couple weeks, and in too much pain to ride for a week.
Also, its easier to stop a rear. Generally bucking gives a horse momentum for each following buck, which is why horses revert to bronco bucking when they get upset. I feel like it requires little thought, and in little time, their rider is off. Rearing however, often has some other motivation. It requires too much effort, concentration, muscling, and plain old talent to be able to do multiple times in a row, and with enough magnitude to unseat you. There is downtime between rears, time for you to prepare, time for you to nip it in the bud and push them through it. If the horse is good, and throwing a playful buck, then yes I'd rather ride that. However if the horse is trying to throw you off, I'd rather ride a rear.
Also, I think a lot of times, young or green horses pull rearing because they may feed off a rider's lack of confidence. (I think thats the reason my filly reared with me, after the first time she did it, I was terrified she'd do it again, and so on. Eventually I realized her rearing was less scary than her bucking, and I was determined to woop her little butt into shape and getting her to respect me. After I decided I'd rather take my chances, than be pushed around by her bratty behavior.. she eventually got the hint, with the little help from a martingale and check, she no longer bucks or rears.. and I can ride her in minimal gear, she won't even try it)
Horses who are naturally independent, confident, and I'd say "intermediate-advanced rider horses" (even after they're fully trained) are more likely to feed off a rider's internal state and play games with the rider. They sense your nervousness or scared, and they think if I rear, I wonder what she'll do. Then they realize you got even more nervous, and eventually they think "If I rear, I'll get out of doing work" etc. Rearing scared me more, for the same reasons it did a lot of you. I had only ridden a rear on one other horse, it was new and scary because it was a different outlet of power I had never experienced before.
However if you recognize rears for what they are, they really aren't that scary. If the horse is spooking, its probably only going to be one powerful rear, if your on your A game, you should catch the horse spooking before it rears and anticipate what to do as the rear happens. Once the rear happens, they may bolt, which I think is more dangerous than rearing. However if its just plain old counterproductive behavior, they aren't going to be so high (depending on your horses balance and muscling) or scary, and a little confidence and scary voice should scare it out of them. If its a bad response to the bit or rider error, then fixing the rider error should fix the rear.
Bucks are way more unpredictable and dangerous IMO.