That's a great question and very common. There are only two main differences between the two tents. Model 6121 is simply the basic version of the cabin tent. Model 6133 is the deluxe version with the massive awning. That's the difference. Model 6121 does have an awning, but it does not have a large deluxe awning. Model 6133 has the basic awning same as model 6121, but also has an additional deluxe awning (a total of two awnings). If you decide to purchase model 6121 please keep in mind that the awning cannot be purchased afterwards. The reason being, it is sewn onto the tent during the manufacturing process. So, model 6133 has that deluxe awning sewn onto it.