Here's my 10p.
Air ride has an ease and practicality that coilovers try to highlight as their selling point: height adjust ability. Air ride does this from the comfort of your drivers seat with the push of a few buttons, where as coilovers involve a morning on the drive way to change the ride height. What coilovers do have is better handling credentials, a good kit (with some time invested) will transform any chassis, the mk4 Golf being a good example of such effects.
Price wise, for a decent set of 2-way adjustable coilovers you're looking at nearly £1400, where as the cheapest air ride is the wrong side of £2000. Each have plus points and each have negative points, for myself it's coilovers that won out as I can't afford air ride and ultimately I want pure handling over all others.
As for the "which handles better", that's a subjecting and relative term: Air ride "handles" better in everyday life than coilovers in a sense whereas coilovers would "handle better" on a track. Reviews/research endorsed by a company for PR reasons will always be bias, regardless of their claims otherwise.