As far as durability is concerned, I have found spray bombs to be decent, but again, it is all about prep. I had a Rocky Mountain (mountain bike) that I repainted, I sanded the original powder coat (I found that removing powder coat completely is more trouble than it's worth) used DP-40 primer out of a gun, but my finish coat was Rust-Oleum white enamel from a can. That bike endo'd and bounced down the trail without me more than a few times... and the paint held up great.
On the other hand, my first lowrider I built, my dad painted it for me with DP-40 primer, and R-M base/clear, all out of the gun... that was an awesome (shiny) paint job, but it chipped just from looking at it wrong.
I think the thing with rust paints is that they always stay a little soft, which resists chipping. Good for something that gets knocked around a bit like a bike.