It seems that the names are used interchangeably, depending on the vendor. "Uchiki Kuri Squash is known by a variety of names. It is commonly known as Potimarron or Onion Squash because of its shape, and is also known as Japanese squash, Orange Hokkaido or Red Kuri squash. Once again we have the Japanese to thank for its development."

also Blue Kuri - the kuri squash, along with Crown Prince. are the best tasting squashes I have come across (and I have tried lots) There is a new hybrid, bred for the british market - Autumn Crown, a hybrid between butternut (which does not always ripen in the UK) and Crown Prince (which is much faster and nice to eat) AC is smaller than CP though, at around 1-2 kilos

Hi, I've grown Potimarron and Uchiki Kuri. They are very similar looking but different sizes. Potimarron is about the size of a soccer ball, and Uchiki Kuri is about the size of a tennis ball. They have very similar flavour, so I'd grow Potimarron because you get more bang for your buck. Here in the UK, Crown Prince has the best reputation, and I've had a lot of success with Zucca Tonda Padana (soccer ball sized with ridges) and Sweet Dumpling (tennis ball sized). Cheers!

These are all very alike, but all are individual open pollinated strains

Uchiki kuri is around 1kg, potimarron about 1.5-2.

Many seed companies are running the misinformation that they are just different names

They are very alike, so get whatever you can.