Remember that the child will be sitting for quite long periods in the beginning before they master the technique, so comfort is important. A small potty is very practical for trips and easily hidden away when not in use. The toilet seats that you attach to the toilet make life a lot easier for the parent, as clean up is simple, simply flush the toilet. However, for the child it might be a very big step and almost scary to be up on the toilet, so a gradual training starting with a floor model is often preferred. Some potties are made so that the top later becomes a toilet seat and the bottom usually then can be turned over to function as a step stool.
Toilets come in different shapes and sizes, with the round and elongated being the most common.
Most toilet seats on the market are made to fit the round seats and therefore do not always fit the elongated very well. A proper fit is important as the seat otherwise will move around, making the child feel insecure. Old wisdom around potty training says that if you have a boy you need to have a splashguard. Therefore, a good splashguard should be a part of all potties, as well as toilet seats. A softly shaped splash guard that is molded into the product is preferred, as loose splash guard attachments have a tendency to become toys and not be there when needed.