When comparing 13th Age vs Heroes Against Darkness, the Slant community recommends 13th Age for most people. In the question“What are the best tabletop RPGs?” 13th Age is ranked 27th while Heroes Against Darkness is ranked 33rd. The most important reason people chose 13th Age is:
The world is half built, letting you get in and leave your mark. Each class plays mechanically different than other d20 versions. Skills are placed by backgrounds. It's a short hand and interesting way of playing DnD.
Ranked in these QuestionsQuestion Ranking
Pros
Pro The game is built for people who've done it before
The world is half built, letting you get in and leave your mark. Each class plays mechanically different than other d20 versions. Skills are placed by backgrounds. It's a short hand and interesting way of playing DnD.
Pro Long lists of skills are gone completely
And covered by backgrounds (much like FATE or Cortex+) so that players aren't searching through lists of skills and what they can do constantly.
Pro Gonzo without the grid
13th Age has some very gonzo fights with party combos, lots of variable powers for monsters and PC's but as a simple set of rules for combat that speed it up without losing a lot of options.
Pro Focuses on simplicity
The game uses a single "d20 + modifier ≥ target" mechanic for everything. Characters can be created in less than 5 minutes. The writing is concise and clear.
Pro Deep, without being cluttered
A lot of meta-tools such as templates, etc, that make combat encounters incredibly simple to construct. Great tools for creature-building. A lot of good information on world-building. You can make any type of game efficiently, from hack-and-slash to role-playing. If you have played in a D&D campaign, this is a great choice for your first outing as a GM.
Cons
Con Too similar to 4th
Con The Icons and the PC relationships to them can confuse
Can be confusing, especially for new players.
Con It doesn't really do anything new, it just looks pretty
Con Requries prior knowledge of RPGs to completely understand
Some knowledge will be required to understand the rules as there are some unexplained conventions that are presumed to be understood.