When comparing OpenGameArt vs TexturePacker, the Slant community recommends TexturePacker for most people. In the question“What are the best sources for textures for game development?” TexturePacker is ranked 1st while OpenGameArt is ranked 2nd. The most important reason people chose TexturePacker is:
Drag and drop sprites onto the canvas, change the settings, then output.
Ranked in these QuestionsQuestion Ranking
Pros
Pro Committed to free/open licensing
All assets made available through OpenGameArt must be licensed under one (or more) of the following: CC0, OGA-BY, CC-BY, CC-BY-SA, GPL or LGPL.
Pro 2D and 3D art
OpenGameArt has both 2D and 3D art assets.
Pro Big library of varied CC0 assets
OGA currently has an impressive library of free assets, especially in the texture department.
Pro Supports asset requests
OpenGameArt has community forum sections dedicated to Resource Requests and Open Commissions.
Pro Simple Interface
Drag and drop sprites onto the canvas, change the settings, then output.
Pro Multiple Atlas Output Formats for Unity
There are three different outputs for Unity to read the atlas; JSON, Texture2D, and 2D Toolkit.
Cons
Con Mediocre organization and search functionality
The curator of OpenGameArt acknowledges that the tools for finding the assets you need are sub-par. Correcting this is a near-future priority for improvement, and as of September 2014 is the next milestone goal of the site's Patreon campaign.
Con Assets may have restrictive licenses
OpenGameArt hosts art under any of several licenses, some of which may not be suitable for commercial projects or for release on certain distribution platforms. Careful review of which licenses are compatible with your project is essential. The site's search facility allows filtering by license.
Con Pure functionality in the free version, you can't even set margins
The full price is too high for such a simple app.
Con No direct integration
TexturePacker is an external third party application with no Unity Inspector interface.