I brought our big suitcase but I traveled with my husband and pretty much made him roll it around the whole time. We checked it also which made it easier to get through security and I didn't have to lift anything into the over head bins. The big suitcase held both our clothes though so if you are traveling without a spouse I would opt for the smaller carry on suitcase. I'm not sure how everyone feels about carry on but for me I prefer to not lug anything around the airport, less for me to worry about.
Several times people have mentioned the walk across the bordor. This is nothing major. The van stopped we had to walk into the room show our birth certificate, driver license, and run our luggage through a scanner. My husband bought some beautiful knives while we were there and we were dissappointed to find out you cannot bring knives back over the border to the states so they confiscated them...Bummer!
You are also going to want to bring cash, lots of 5's and 1's for tipping and shopping. If you do go shopping you will want to bargain and negotiate, never pay what they are asking.
I found myself getting nauseous the first 5 days after surgery. You may want to make sure you have some liquid nausea medicine on hand such as mylanta or pepto bismol.
I'm sure there is more but I can't think of it right now.