In addition to @beefnoguy’s great explanation, I would like to add some finer points.
What @beefnoguy says about wine glasses applies to many, but not all sake.
Just like wine, a sake’s aroma will concentrate in the bulb and allows you to get a more concentrated whiff.
While this amplifies the attributes of many sake, it can result in an over-concentration for some.
Notable exceptions would be:
Low quality sake The aromas here are simply not ones to be enjoyed (for most people) Aromas from low quality sake tend to be boozy.
Bold sakes Aromas from bolder sake can stand up for themselves. Many times these are best enjoyed at room temperature or warmed. In this case, a ochoko/guinomi would be the vessel of choice. Think yamahai or kimoto.
Masu Some, but definitely not all, sake benefit from being drunk from a non-lacquered wooden masu–made from wonderfully fragrant Japanese cedar (sugi). Tarusake is the most obvious choice here. The Japanese cedar taru cask-aged sake is often best enjoyed straight from a Japanese cedar masu. @beefnoguy expounded on tarusake’s virtues a little farther up the thread. Who wouldn’t want to drink this??
- The woody aroma (and to a lesser extent flavor) that is imparted by the Japanese cedar masu can get in the way of more subtle aromatic notes. For this reason, in many cases, it is not a good fit for daiginjo-grade sake.