BMX for my 8 year old

My son is 8 years old and I just bought him a BMX bike. We live in the city and he rides around mainly in our complex, and sometimes to the park. We don't do any long distance riding. He's a big kid for 8 and very hard on bikes. When I told this to the guy at the bike store, he steered me away from a gear bike and said that a BMX bike would be a wiser choice. Both the gear bikes and BMX's were in the same price range. He said that if my son threw down the gear bikes, they would be much more expensive to fix. And since we don't live in the mountains, I didn't think he really needed gears. With the type of riding he does, I'm certain that after the novelty of gears wore off, that he'd most likely leave it in one gear most of the time.

He and his twin sister have been enjoying the back pegs for giving rides, but he still gripes about not having a gear bike. Last night he was riding to the park and one of the front pegs got caught in a fence and he flipped over the handlebars....

I've been second-guessing my choice here. His sister is due for a bike soon and if the BMX was a mistake I don't want to make it again. Seems like a cool bike, but was wondering what you thought.