The pilot reported that the motor-glider encountered a wind gust during the landing flare that resulted in a 15-degree runway misalignment. The pilot considered a go-around, but elected to attempt a landing in the grass adjacent to the runway as the safest course of action. He stated that another wind gust "caught" the right wing and the motor-glider ground looped in the grass. The motor-glider subsequently nosed over and received substantial damage to its fuselage. The pilot reported no mechanical malfunctions or failures. A weather reporting station near the accident airport recorded the wind speed as 15 knots gusting to 25 knots. The reported wind direction was aligned with the runway direction.