Provided the car was washed regularly to remove salt during the colder weather months, it should last OK. Both cars will have known rust points, but rust usually starts from stone chips or a build up of dirt / debris / rotting leaves that allows water to linger or to get to places it shouldn't.
Short journeys are not very good for cars - the engine will have hardly any time to get up to temperature - exhausts will rot out as they won't get hot enough for condensation / moisture to dissipate.
Leaving cars idling to warm them up as well isn't really that good for them either.
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