Jackson KM, Cook TM. Anaesthesia. 2007 Apr;62(4):388-93
The airway arm of this trial compared devices including i-gel, Cobra, SLIPA and Laryngeal Tube Suction II. Each device was inserted twice into each manikin by ten anaesthetists, with each insertion scored and ranked. No one manikin outranked the others for all devices. i-gel insertion was 'significantly the easiest'.
Link to abstract