Daiginjo is the most expensive sake as it uses only core part of rice; more than half of the rice should be polished to make daiginjo. But there are two types of daiginjo which are junmai-daiginjo and plain daiginjo. As we learned the difference between junmai-shu and jozo-shu, now you can guess junmai-daiginjo should not contain added alcohol. Plain daiginjo is made of water, highly polished rice and added alcohol and is a part of jozo-shu.
Then quality of plain daiginjo is lower? Not necessarily. As mentioned, alcohol is added to adjust the flavor or taste, and whether to add it or not depends on regional preferences. Taste of sake is tightly related with local culture and cuisine and some local cuisine require the taste of jozo-shu rather than junmai-shu. Same logic can be applied to junmai-ginjo and ginjo.
Now you understand six types of sake as above. You can find the difference by checking the word of “醸造” jozo-shu is labeled or not (which means, if alcohol is added or not) and the percentage of rice polishing (more than 50% is daiginjo, 30-50% is ginjo). So, next step is to try all types and find your favorite!