There is a lot more usable space in the back of the smart than there is in the front of a bug. I have yet to come home with too many groceries, for a household of three adults.
Now, I have had a crowd form to watch me stash everything in the back of my smart, and drew a number of surprised comments that I could get a buggy-full of stuff in the car, and still have room for me!
Just a word of advise - heavy stuff on the bottom, bread and chips last...