To choose the best canning pot, you should look for one that is deep enough for the size of the jar or jars you want to use and large enough around to fit as many jars as possible. While canning, you need to be able to fully submerge your jars, which means you need a pot that is also deep enough to contain a small rack at the bottom. You should also look for a canning pot that you can fit multiple jars into at the same time, without them touching.
One of the first things you should look for in a canning pot is its depth, with consideration for the sizes of the jars you are going to use. You should look for a pot that includes a rack you can place at the bottom, though you may be able to utilize a rack you already have for this purpose. As you look at different pots, look for one that is tall enough for the short rack and still have the jars stand upright while covered with one or two inches (2.5 to 5 cm) of water. You need to fully submerge the jars, and a pot that is not tall enough may boil over during canning.
As you are considering pots, you should also make sure to choose one that is wide enough for your purposes. You should be able to fit a number of jars in the pot without them touching. If you are using a smaller pot, then you can include fewer jars at a time, but that extends the period of time you are going to spend canning. You should choose a canning pot that is wide enough to accommodate multiple jars, but not too wide for the stovetop burner you plan to use.
If you cannot find a canning pot you like, or do not want to spend money on one, you can always use any type of pot you already have that meets your size requirements for canning. You can use a rack from a crock pot or dehydrator or cooling rack to place at the bottom. If you are looking for a pressurized canning pot, then you should find one that meets your size needs and can provide you with the controls over internal pressure that you prefer. These types of pots are used for canning foods that are low in acidity and are more specialized than water bath canning pots.