there are many options for frame materials. I have a 531 steel commuter and a alu bianchi racer. I think steel has a better ride and is definately heavier, but is very durable and fun. + thieves dont really go out of their way to steal a bike with lugs and so on. The bad part is that no matter what talk there is about fatigue or this and that about steel v. alu, steel WILL RUST. I had another 531 frame rust out on me (literally) and I am wary of that. but steel is usually cheap and is very well built (pre 90s) in most cases. To be honest modern alu is cheaper than modern steal, which is regarded as somewhat boutique. so i dont know, make you choices given the options.