rotorspeed
But offshore or from a raised helipad there is a huge difference. Climbing to 20 to 30 feet, probably with some lit part of the structure visible as a reference for the climb, a rotation that then guarantees you clear the initial ground obstacle and continue forward to try and gain airspeed in order to fly away - the 50 - 300 feet height, above sea level at which you begin is used to do that, and unless operating at a low helideck elevation at max all-up (which your ops manual probably prohibits) then even in the event of OEI you will fly away using slightly more nose down than standard 5 - 10 degrees for departure.
Onshore you have the obstacle of the ground always in front of you, or obstacles around you, and so without the required visual cue during a longer portion of the procedure ..... it quickly goes wrong if you do not follow the profile, or exceed pitch attitude references
It can go wrong offshore too, but there is more time to react / correct / monitor