The Impala has 18.6 cubic feet, the Escape has about 30 cubic feet, although that's simply because there's more vertical space in the trunk. I don't know the Escape well enough - if it comes with a cargo cover and you want to keep your luggage out of sight when the vehicle's unattended, there's probably more room in the Impala.

Between the two, I'd go with the Impala. It's a much older design, but it gets decent mileage (probably better than the Impala when fully laden) and is a comfortable cruiser. As a grown adult, I'd probably prefer to be in the back of Impala for a long trip.