Newer second generation supraglottic airway devices may perform differently in vivo due to material and design modifications. We compared performance characteristics of the Ambu® AuraGain™ and LMA Supreme™ Second Seal™ in 100 spontaneously breathing anaesthetised patients in this randomised controlled study. We studied oropharyngeal leak pressures (OLP) (primary outcome) and secondarily, ease of insertion, success rates, haemodynamic response, time to insertion, and complications of usage. We found no significant difference in OLP between the AuraGain versus the LMA Supreme, mean (standard deviation, SD) 24.1 (7.4) versus 23.6 (6.2) cmH2O, P=0.720. First-attempt placement rates of the AuraGain were comparable to the LMA Supreme, 43/50 (86%) versus 39/50 (78%), P=0.906, with an overall 98% insertion success rate for the AuraGain and 88% for the LMA Supreme after three attempts, P=0.112. However, the AuraGain was deemed subjectively harder to insert, with only 24/50 (48%) versus 37/50 (74%) of AuraGain insertions being scored 1 = easy (on a 5 point scale), P=0.013, and also took longer to insert, 33.4 (SD 10.9) versus 27.3 (SD 11.4) seconds, P=0.010. The AuraGain needed a smaller volume of air (16.4 [SD 6.8] versus 23.0 [SD 7.4] ml, P <0.001) to attain intracuff pressures of 60 cmH2O, facilitated more successful gastric tube insertion (100% versus 90.9%, P=0.046), and had significantly decreased sore throat incidence (10% versus 38%, P=0.020). One AuraGain and six LMA Supremes failed to be placed within the stipulated 120 seconds trial definition of 'success'; these patients had risk factors for failed supraglottic insertion. In conclusion, both devices had similar OLPs and performed satisfactorily. However, the AuraGain resulted in less postoperative sore throat despite being harder to and taking longer to, insert.