Is a spray faster and easier to use than a felt roller (generic Lubri-disc) or a pad type applicator (No-Drip from Finish Line or No-Mess from White Lightning)?
Refillable multipurpose aerosol can from walmart (SureShot alternative):
Supposedly most products sold as sprays can be purchased as liquids and used in one of these for about half the cost. Does that hold true for bike lubes?
Pad/felt applicators are easier to use and faster between the two, if those were the only options. If the intention is to easily do a good job and not leave a mess, spray application for bicycle chain lubes is last place compared to essentially anything else.
Sprays require care and extra steps to keep the lube from getting where you don't want it (brake surfaces especially, but also everything you don't want to have an oily residue like your cassette, derailleur, frame, the ground, etc.) They also invite over-application - the ideal amount of lube for most bike chain lubes and most situations is one drop per link, or potentially two or three for certain ones and/or in certain situations. While possible, they make it it more difficult than most other options to control the volume coming out. This is not to say sprays don't or can't work, but the question is about relative merits and they mostly don't have any.
There are nice things about pad applicators, i.e. it is true they reduce wasted lube, but they get dirty quickly and need replacing. Also the notion of wiping lube on to a chain like they do doesn't work equally well for every lube; thinner and more penetrating ones can creep into the inner parts of a chain when applied that way, but mid-weight or thick ones wick in better when applied as a drip down the middle. Meanwhile, good technique with a drip bottle makes waste very minor for most lubes.
The reason most people use drip application for bike chain lube is not economy, it's because it's the least hassle and gives the best results.
I prefer the old fashioned one drop per link. Less waste, no lube on undesired places. Better economy, less use of dubious chemicals. Aerosols almost by definition increase the amount/risk of inhalation and getting it into eyes/nose isn't good either.
In the current winter-salty-slush season I've been using dry lube not bothering to protect the side plates from corrosion with any (oily) lube. Sure, the chain looks corroded and awful, but it runs smooth as butter and will wear down long before corrosion ruins it anyway.
Sprays and quick applicators might be faster, but are IMO worse than single drop technique in most other aspects with regards to lubing the chain.
