I've flown a bit on both types (about 2,500 hours on the S-76, including a few hundred on the 'B' and probably about 3,000 on the A109). The S-76 is obviously a considerably bigger airframe and doesn't have the good downwards/forwards visibility of the A109. But an even better A109 variant to use for this type of operation would be either the 'S' or the 'SP'. Both have a longer cabin, meaning slightly more passenger legroom and a MAUM of 3175kgs as opposed to the 3000kgs of the earlier versions. Both approved for elevated helipad ops and have a very good power reserve. Most later examples of the 'S' and 'SP's have a disposable payload of about 950 kgs and burn about 225-230 kgs of fuel/hr at 145-150 kts.