The key here is to take a pragmatic approach.

If the consumer will likely just need id's, then the first approach is good

If the consumer will need data in addition to id's, then the second approach is good

If both of the above options are used heavily, then implement the second approach and implement field filtering[1] on top

[1] - http://www.vinaysahni.com/best-practices-for-a-pragmatic-res...