He replied, "One comes with software, the other doesn't."
"Doesn't this one have an internal modem, and the other an external?"
At this point I wasn't feeling much confidence in his knowledge, especially since I recalled both boxes listing the same software. He then advised me that I would have to call Telus before buying a kit to reserve a port, if one was available in my area. I thanked him and left. Telus has their own store, and I think I will go there tomorrow and see if I can get more helpful service. I hope it is open on Saturday...