Match the scope before comparing totals
List the proposed panels, inverter and battery using the exact model names shown on each quote. Add rows for mounting, protection, delivery, labour and commissioning. Ask which work is included and which depends on a site visit.
Ask what gets handed over
Request a description of the proposed backup circuits and the documentation you will receive. Ask who handles service and how to report a fault. If the quotes give different runtime estimates, ask each installer which appliances and usage hours they used to arrive at them.