Ginger jar or vase, do you know the difference?

I collect the Japanese vases and ginger jars. Most of them are the cobalt blue, others are the same style only black, cream white, white, yellow, burgundy or green. My question is how can I tell the difference between a ginger jar that has lost its lid and a vase? I know that if there is a gold layer at the top of the neck it is obviously a vase, but what if the gold has been worn off from use? I have attached a picture of what I believe are 2 ginger jars with missing lids and a vase (the latter is the one on the right). My guess is that ginger jars ALWAYS have a straight neck instead of a fluted or curved neck but I'm not positive. Is there any way to know visually how to distinguish a ginger jar and a vase?