It doesn't matter which platform you're playing on Portal 2 is hands-down one of the greatest video games of all time and definitely one of the best Mac games ever. Therefore, you can buy heroes, skins, and mounts in the game with USD.
You can earn gold in the game, but to get anything decent will take a looooong time. HotS is free to play, but you'll be stuck with the playable characters offered to you, which rotate every week. Made by Blizzard, this is one of the best ARTS games around, with awesome characters, solid voice acting, great graphics, and necessary teamwork that doesn't make you want to drive your Magic Mouse through your 5K iMac screen. Not the case in Heroes of the Storm, where if one team member isn't up to snuff, the rest of the team feels it.
Many MOBA-style games have the same problem: one person can be a hero and win the game on their own while screwing over the rest of their team. You'll have to destroy opposing team members, as well as their structures to gain points for your team and ultimately win the match. Heroes of the Storm is a MOBA game in teams of five fantasy characters battle against one another for supremacy in a series of different game modes.
