Really depends on the person and horse, I'd say!
Arabs are VERY sensitive and responsive. They can also be airheads. Mine, Maverick, is awesome! What I've learned from working with him is that you have to ASK not TELL. If I ever tell Maverick to do something he throws his head, arches his back, bucks, prances, puts up a fit, etc. If I ask him, however, he's awesome! He responds quickly and in a genuine, kind manner. Like every horse though, you can't take that as an excuse to not be a firm rider. You've gotta be as soft as you can, yet if they're being bratty, you've gotta make sure that they know that it isn't acceptable. Usually I'll respond with a quick tug of the rein or pushing him forward a LOT. That way they don't have much of a tantrum.
I watched a professional lesson done once...My trainer's match haha My trainer was getting a lesson on one of her new horses who was a saddlebred/arabian. The thing with my trainer is that when she wants something from a horse, she asks but if she doesn't get that thing she makes sure that the horse knows that it's wrong. Her hands aren't very soft and if the horse is spooking at something she'll turn the horse towards it and make the horse walk towards it. It DOES make sense, however what the other coach was saying was that Arabs are a breed with a VERY good memory. If they spook in one corner they're going to remember that and if you make a big deal about them spooking they'll remember that there's something to make a deal about there. The coach was saying how instead of making the horse go towards it, you've gotta completely ignore it. Think "Hm, I'm not sure why you aren't staying on the rail" even though you know what the problem is. That way the horse won't see it as as much of an issue the next time. So she was getting her to drop her hands, keep soft fingers, ask and release, ask and release.
It's sensitive things like that that make the breed difficult. They're smart!
However, as intelligent as the breed is, there are always those airheads that just don't know what they're doing and why they're doing it. My friend has an Arab who is just a big dummie. He'll run around with his head in the air and doesn't really think about anything that he does. He's not really the smartest of the pack for sure.
My horse Maverick is amazing though. He's a natural jumper and I started him on barrel racing and games and stuff a while ago and he is SUPER speedy! He gives quick turns as long as I sit and let him turn instead of using my rein to guide him through it. He's a very spooky horse, but if he wasn't, he'd make a great cowhorse. He stops and turns and does rollbacks on a dime! I'm also showing him in English and Western Pleasure and we won high point at our last show! He can be super calm and lazy, but mostly, he's super jumpy, jittery and energetic. Not totally sure if that's because he's only 6 and has no experience or because he's an Arab, it's hard to tell.
Anyway, if you're a patient rider who wants a challenge, I'd definitely recommend and Arab. They're a beautiful and magnificent breed! If you aren't a big fan of taking your time and being relaxed through training, the Arabian is definitely NOT for you.