예요 is a shortened form of 이에요. So 이에요 is actually the same as 예요.
The difference is that you cannot shorten 이에요 to 예요 when the noun before it has no 받침.
사과이에요 (O) 사과예요 (O)
(사과이에요 is technically not wrong, but we commonly use 사과예요 only)
학생이에요 (O) 학생예요 (X)