Yeah, I used to lean towards an external map editor like LDtk thinking, "They get to spend all their time on the editor to make it nice, so that ought to be nicer than what I'd make while having to work on the game, too.", but after using an integrated editor that can show me the schools of fish that i just added to the game, in all their glory with the animated movement logic, while playing the game! I changed my mind and decided that in-game editing was one of the most useful and nice features, that an external editor could never provide.