JP Magazine did a test and write up on them sometime ago - it turns out there were some big differences between the different intakes. This info is from jpmagazine.com
Stock Jeep
Install 1-10: 10 (bolted on just like stock)
Filtering Element: paper and foam
Average Peak Torque:188 lb-ft
Average Peak Horsepower:142.3 hp
Pros:
installs great
filters really well
high resistance to water intrusion into engine
Cons:
paper element falls apart when wet
doesn't flow that well
it is a stock part.
Mopar intake
Msrp: $359.00
Install 1-10: 8
Filtering Element: Cotton Gauze
Average Peak Torque: 199.8 Lb-Ft
Average Peak Horsepower: 155.6 Hp
Pros:
Well-thought-out kit, with all the parts needed, and then some
Has factory backing. No more possibility of warranty denials thanks to intake kit.
Can get parts for it, as well as oil and cleaning kit at
dealers nationwide
Cons:
With the throttle body spacer, it can be more difficult to install than others
Same issue with cold air separation as the aEM kit (large space at the area behind the filter near the under hood fuse block)
Included hose clamp doesn't fit pCV hose at the intake tube
Airaid intake
Msrp: $399.82
Install 1-10: 6
Filtering Element: Cotton Gauze
Average Peak Torque: 200.9 Lb-Ft
Average Peak Horsepower: 154.0 Hp
Pros:
Gradual taper on intake tube
Good power numbers
unique design has filter bolting to coldair mount on one side, and tube to the other. Tube doesn't actually bolt to filter.
Cons:
Child-sized screws for cold-air housing
requires removal of valve cover bolt for a brace
requires removal of underhood fuse block, fuse block bolt, radiator bolt-in rust areas, this could be a problem.
AEM
Msrp: $362.71
Install 1-10: 8
Filtering Element: Synthetic Dry filter
Average Peak Torque: 198.4 Lb-Ft
Average Peak Horsepower: 155.1 Hp
Pros:
no oiling needed-easy cleaning in a bucket of water or smacking on a bumper
among the best filtration of aftermarket conical filters
all parts needed for install were included, with extras to boot
Cons:
With the throttle body spacer, it can be more difficult to install than some others
halfhearted attempt at separating ambient engine air from the intake (the area between the under hood fuse box and the filter is largely open
we'd stain the bright-white filter on the first
off road trip we took.
The Mopar, Airaid and AEF were the best. If I were going to buy one, it would probably be the Mopar.