do you want an anecdotal or empirical comparison?
Here's a thread that compares the two - I've included the measurements as well:
http://www.jeepsunlimited.com/forums/showthread.php?399103-Jeep-Unlimited-vs-Mercedes-Gelandewagen
................................Jeep JKL.....G500
Headroom fr......................41.3.....42.2
Headroom rr......................40.4.....40.0
Hip room fr.......................55.6.....51.5
Hip room rr.......................56.7.....53.9
Leg room fr.......................41.0.....52.5
Leg room rr.......................37.2.....41.9
Shoulder room fr................55.8.....53.7
Shoulder room rr................56.8.....56.3
Front Volume.....................54.6.....44.5
Cargo Room.......................46.43....45.2
Cargo Seat Folded..............86.75....79.5
Wheelbase........................116......112.2
Track fr............................61.9.....59.6
Track rr............................61.9.....59.6
Overall Length...................173.4....185.6
Overall Width.....................73.9.....71.3
Overall Height....................72.3.....77.8
Overhang fr.......................26.7.....36.7est
Overhang rr......................30.6.....36.7est
Turning Circle....................41.2ft....43.5ft
Ground Clearance fr............10.5in....8in
Ground Clearance rr............10.1in....8in
Approach Angle..................44.4d.....worse
Departure Angle.................40.5d.....worse
Breakover Angle.................20.8d.....worse
Weight.............................4315 lbs.....5545 lbs
Engine...............................V6........... ....V8
HP...................................205hp........ .292hp
TQ...................................240lb-ft.......336lb-ft
Fuel Requirment..................Regular.........Premiu m 91 Octane
4X4 system.......................Part-time.........Full-time
Transfer Case Ratio.............4.0:1.............2.16:1
Axle Ratio..........................4.10:1...........4. 38:1
Lockers.............................Fr/Rr............Fr/Rr/Center