I'm obviously biased, (especially because my product can't be made into an aerosol), but I consider aerosols far too wasteful for chain lubes. First of all there's a very high ratio of packaging material and propellant vs. actual product. Secondly because a higher percentage will be wasted in overspray missing it's intended target. You'll find that you consume those 6oz cans in far less time than you used to consume the 4oz. drip.

If you follow up a normal drip-on application by wiping off excess, your rag or towel will pick up some lube and spread it onto the plates as rust protection. If it isn't providing enough protection, adjust how you apply it, or use it more often.

Regarding rust. None is best, though a bit of surface rust here and there is usually meaningless. But if the chain is allowed to continue rusting, or allowed to rust internally, it'll definitely cut into it's usable life, and in more extreme cases can weaken it enough to snap under load.