Gel electrolyte batteries typically have a higher internal resistance than AGMs, so you would expect 'SiO2' batteries to have a higher internal resistance and higher voltage drop under load. Furthermore, the internal resistance rises as the SOC decreases (all batteries) and lead acid voltage decreases rapidly with decreasing SOC, leading to the shutdowns you are seeing.
LiFePO4 has a lower internal resistance to start with (although the BMS can add some resistance), higher starting voltage and very little decrease of voltage with decreasing SOC, making it better suited to high load situations.