From a Japanese Dictionary:
夕 means the time when the sun sets. But, 夕 is not used in modern Japanese. It is only seen in classical texts.
夕方 also means sun setting time, but 夕方 is used in modern Japanese.
Note that 夕方 has antonym: 明け方. 明け方 means sun rising time.
This word has many meanings:
晩 is 夕方, but 2. says
晩 is night.
And so, 晩 (3. means 晩 is dinner) is used to express a wider span of time.
夕べ is 夕方. 2. says
A night with some event. 3. says
I think 2. is the most common usage and 3. is not used very often because the other word
昨晩's pronunciation is the same. However, because 夕べ also means 夕方, 昨晩 is preferred.
Note that 昨晩 has two ways of reading it:
yube (same as 夕べ) and
夕方 and 夕 are almost the same, but 夕 is used only in a literary style. 晩 means a later time.