The pricing difference may depend on which few days you need it for. A moving van
rental on the weekend may be more expensive than just renting for a few days during the week. (company links open in a new window)
I checked for a price for a cargo van for 4 days on a weekend, the price for 4 days through the week and then checked the rate for a weekly cargo van rental. The length of the rental made no difference... the daily rate was the same for each rental period. You may find a different result with another company.. the only way to know for sure is to check multiple suppliers.
The first thing that I suggest you do is research what weekly cargo van rental suppliers are in your area; then you can start looking for pricing for the type of truck rental you want for the dates you're looking for, checking the difference for each supplier for a moving van rental for a week vs renting for just the dates that you need.
I did a yellowpages.com search for cargo van rental and moving van rental for Hartford, CT and found the following companies:
Long Distance Movers(888) 631-34403 UHaul Locations
U-Haul Center Of Main St 3197 Main St
U-Haul Center Of West Hartford 164 South St
U-Haul Neighborhood Dealer - 3 B's Hardware Supply 301 Franklin Ave (860) 296-2683
5 Budget Truck Rental Locations
125 New Britain Ave (860) 522-0580
300 Center Rd (860) 296-2167
39 Jennings Rd (860) 249-2700
430 Tolland St (860) 289-0010
455 Wethersfield Ave (860) 296-3377
3 Penske Truck Rental Locations
10 Locust Street (860) 527-6696
1005 New Britain Ave (860) 953-7712
24 Andover Dr (866) 957-0046
2 Ryder Truck Rental and Leasing Locations
185 West Service Road (860) 241-4354
99 Murphy Rd (860) 493-7426
Hope this helps!