Network – Load Balancing Performance: Sophos vs. Cyberoam

The results CR35iNG – 10.6.4 MR-1 and Sophos XG135 (SFOS 17.5.3 MR-3) are side by side and the load balancing comparison results are presented below:

Load balancing test with Sophos help
Load balancing test with Sophos help

Load balancing test with Cyberoam
Load balancing test with Cyberoam

I've already set the round robin method on Sophos:

define the wan-load-balancing weighted-round-robin routing

Both UTM are sitting next to each other and I just replaced my nic gateway to test them. There are 4 modems, 100 Mbps DL / 10 Mbps UL each. As you can see, Sophos is still slower than Cyberoam. What could be the problem with Sophos here?