Regarding the technical specifications, according to Schiebel, the UAS is 4.8 meters long, 1.9 meter high and 0.9 meter wide. It can fly at a maximum speed of 120 knots (cruising speed 55 knots). Size apart, the true difference compared to the S-100 system is the payload capacity. Indeed the S-300 is able to carry up to 340 Kg (fuel including) and its maximum take-off weight can reach 660 Kg. This is basically three times more compared the S-100 can carry. With a 50 Kg payload, the S-300 can fly up to 24 hours (4 hours with 250 Kg).
The French Navy’s VSR 700 UAV mentioned in the last paragraph as a competitor for the S-300 was discussed here.