Sliding gates and swing gates serve the same function — closing an entrance — but call for very different structures, with direct implications for the quote that go beyond the customer's aesthetic preference.
The sliding gate: a running structure
A sliding gate needs a track at ground level or overhead, a suitably sized motor if automated, and clear side space for it to open fully. The gate itself has to carry its own weight in cantilever while it runs, which often calls for a sturdier frame than it appears to need at a glance.
The swing gate: hinges and fixings
A swing gate instead needs correctly sized hinges and solid fixing of the posts, but no track and no clear side space. Installation time is generally lower, though how well the hinges last depends heavily on the quality of the ground fixing.
What changes on the quote
Material, installation hours and, where automated, the type of motor required all differ appreciably between the two. Presenting the customer with an explicit comparison of the two options, and what each costs, helps the negotiation more than imposing a choice without explaining the practical implications.