Make the scope comparable
Check that each proposal states the exact panel count, panel model, inverter, mounting approach, battery usable capacity and major electrical work. A lower total may simply exclude work included elsewhere.
Separate product and workmanship cover
Product, performance and workmanship warranties cover different things and may come from different organisations. Read duration, exclusions, claim process and whether any cover depends on installer or manufacturer conditions.
Treat the survey as a decision gate
Before signing, make sure the survey outcome, final layout, predicted generation, grid process, payment schedule, cancellation terms and changes procedure are recorded in the contract.