Ah, rice! The Japanese are very particular about their rice! They can tell the difference between rice grown in their local prefecture and rice from the next.
Like any other grain crop, the flavor of rice will vary depending upon growing conditions, the seed grain, and storage. The weather, the water...they have an effect on the resulting rice grains.
You can buy the same rice brand (for example, Nishiki) but the crops will taste different depending upon in which season they were grown and harvested. You see, most of the "Japanese" or short grain rice available here in the US is grown in California or Texas.
Check the label on your rice bag because the grades vary. Lower grades will contain broken grains of rice which will cook up with a different, mushier texture than whole grains.
Currently, one popular type of premium rice is considered to be koshi hikari. Because of the climate/environmental problems of late, rice prices have escalated!
Buy your rice where rice sells. Otherwise, you'll be purchasing rice that might be sitting on shelves for a long time. But not all Asian markets are the same. In my local Asian market, mostly frequented by Vietnamese or Koreans, the Japanese rice (short-grain) does not sell as quickly as other varieties of rice (glutinous, long-grain, etc.)