I agree with WSArabians. I would of course say, Neither! Go with an appaloosa! But, it is up to you. Which horse you 'click' better with. There are so many horses you can look at, but then you will find one and say, 'hey,' and then a moment of silence. Then you know that's the horse.
I would suggest go meet them. Not just ride, but brush, lead the around. You either like their personality or don't. If you have already done that, and still, can't decide research the breeds to find stuff out about the breed in general.
I can't make the decision for you, and let me tell you, with my new horse (2 1/2), I loved him the first two times I rode him, then he reared and did stuff totally unexpected. I thought I had made the wrong desceion (I butchered that word), but I had already paid for him, and so on. His owners are really nice, and they are working with me with him. Me and Bo have stronger bond now. But that happens with any horse, and I take it you are a first time horse owner, so don't get discouraged quickly when they make a mistake.
Just remember, they are still young, and like to be very testy. Make sure you have access to a trainer or experienced friend. But my Appaloosa has Arabian in him like, 4 or 5 generations back, and the Arabian was mixed with his bloodlines for endurance, loyalty... and something else I think... But I would say Arabian =]