Mainstream vs Independent

Independent Label:

Advantages:
Closer to fans as they can relate and engage rather than making money off of them. The more they are closer to their fans, the more their fans feel their ideas and music to be compelling.
Easier dissemination of music - with the internet as an affordable way to promote bands and musicians, the music of these groups easily reach people with like interests in certain genres of music. Faster publication, not requiring the approval of any higher supervision. 

Disadvantages:
Inconsistency - most independent groups may or may not make it even if they've gained a great set of fans overtime. Financial inconsistency could do great to make or break professional independent musicians.
Music quality and copyrights - another major concern is that without a major recording label, independent groups put their ideas at risk of being copied simply because they have no rights for their music in place.

Mainstream Label:

Advantages:
The artist will be able to reach a wider audience because the record label would have had an existing reputation. 
The mainstream labels will also have enough funds to back advertising, as well as creating tours and an abundance of merchandise.

Disadvantages:
However, this can mean that the artist can lack creative freedom as they are being controlled and shaped into an 'image'. 
The record label can also alter or censor the artists' album as they believe it will sell better, control access of distribution.