IndieDB isn't just a place where you can build hype for your game: it aims to be the definitive place where you should. Everything about the site's features and interface are designed to help devs present themselves, and to kindle user interest in new games.
Desura and IndieDB were initially both operated by Desura Group, and shared a single user database. Linden Labs obtained Desura (only) in January 2014 and the sites' user bases are now split, but extensive crossover remains. Interest built through IndieDB can translate directly to sales on Desura.
Your game on IndieDB has a popularity ranking, but it considers only the past 24 hours, making it only good for noticing spikes in attention. Individual pages have hit counters, which can provide a more lasting record of interest but must be tracked and compared manually.
The contributing editors of TIGSource are free to indulge their personal gaming interests, and frequently promote titles that they feel stand out in some way.
Spontaneous endorsements from bloggers, reviewers and other developers can generate as much or more interest as any direct effort on your part. TIGSource is positioned as a community for indie developers, making it one of the best places to catch the eye of your peers.
TIGSource Forums are designed to support a community of developers, not as an ideal marketing platform. Like most forums, you can start new topics and have limited control over the formatting of your own posts only.
Concepts entries have the same user presentation as regular submissions, including favorites and voting. Steam provides comprehensive popularity metrics for Greenlight Concept titles.