When comparing IndieGameMusic.com vs Freesound, the Slant community recommends Freesound for most people. In the question“What are the best sources of royalty free game assets?” Freesound is ranked 5th while IndieGameMusic.com is ranked 13th. The most important reason people chose Freesound is:
All assets made available through Freesound are required to be licensed under either CC0, CC-BY or CC-BY-NC.
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Pros

Pro Exclusive licensing available
Some tracks are available for exclusive licensing. They become yours alone, and get removed from the track listing.

Pro Supports asset requests
IndieGameMusic.com provides a searchable database of musicians available for project work.

Pro Comprehensive tagging and search facility
Tracks may be searched by artist, genre, mood, license, file type, license fee, and other criteria.

Pro Creative Commons licensing
All assets made available through Freesound are required to be licensed under either CC0, CC-BY or CC-BY-NC.

Pro Extensive asset information
Each sample has a details page which includes a waveform view, a full-length audio preview, user-assigned tags, author-assigned "pack" grouping, and an author chain ("remixes and sources") for derivative assets.
Cons

Con Some assets may have restrictive licenses
Hosted tracks are permitted to enforce a Freeware license, which restricts their use to freeware projects only. The search system allows filtering by license. Track listings are visually tagged with available licenses.

Con Music only
IndieGameMusic.com hosts only full-length musical compositions, not sound clips or assets of any other type.

Con Some assets may have restrictive licenses
Freesound permits uploaders to select the CC-BY license, which disallows the use of DRM, and the CC-BY-NC license, which disallows commercial use entirely. Licenses are prominently displayed on an asset's details page, and represented by a small icon in list views, but there is no option to filter by asset when searching or browsing.

Con Audio samples and sound effects only
Freesound does not host any kind of non-audio asset.
Choice of music is also scant.
