Unreal 4 is by far the most advanced and most friendly user of all game engines an indie developer can have access to. Have the best visual scripting, variety of tools to optimize and profile your games in the editor. Also the best looking PBR out there. And it's FREE.
Unity is a mess in a lot of aspects, and you have to script things. To some programmers is fine, but for artist, and in general is not friendly at all.