I'd vote for the roof rack, which is how I ended up doing it having looked at both. In order to go with a swing-out, there's basically two options: OEM or aftermarket. OEM's the cheapest - swing-outs can be found in the junkyard. The downside is that they can't handle much over a 31" tyre as they're just not designed for more weight. Aftermarket was considerably more expensive as it would involve replacing the rear bumper at the same time, something I'm not looking to do right now.
Another plus for the roof rack - not to mention extra useful carrying capacity.
More drag, definitely, but not noticeably so. Higher COG doesn't seem to have been much of an issue with my setup - but on a DD, a rack plus lift means you might not be able to clear some parking garages. It's for exactly this reason that my spare lives flat inside the cargo area around town and only goes up on the roof if I know I'm going to need the space.
My recommendation would be the Surco
45"x60" rack. The mounts are sold separately, and the ones you'll need are dependent on whether you have the early or later roof rails. They also have a
tyre carrier,
Hi-Lift mount, and
light brackets available. Apart from the light brackets, this is the setup I'm usng and am very happy with it. I plan on adding the
axe & shovel mount at some point in addition to the
extra flooring kit - the flooring that it comes with is spaced slightly too widely apart to securely hold a standard NATO can in place for my liking, even with ratchet straps. Having said that, my rack's carried the spare, 60lbs. of firewood, my 48" Hi-Lift, and 10 gallons of gas without issue on several desert trips, one of which covered approximately 130 miles. Very happy with it.
One thing I will add: do not, under ANY circumstances, get a roof rack that clamps onto the factory crossbars. They're not designed to hold more than about 150lbs. total, and a 31" spare takes up close to half of that number alone; attach to either the roof rails or gutters.