How many people are you traveling with and how much baggage?
According to their website, its says the Nissan is premium car, which would be similar to Ford Crown Victoria or maybe a Toyota Avalon. The luxury cars would be a Cadillac or Lincoln.
If you don't need all the bells and whistles with the premium or luxury cars, I would just to the standard or full size you get just about the same room but not all the extras that you really don't need.
We just have an intermediate rental car, a Toyota Corolla, and we fit 4 adults and one child in a booster seat now problem. We have 2 checked 40 lb suit cases in the trunk and had more room.