Minecraft wiki entry for Hardcore_mode, associated text: For example, the uncharted island in the middle of the sea is easy to control mob spawning on, while in mountains and ravines, creepers descending from heights can more easily surprise you.
A seed with a stronghold inside a mushroom fields biome would make the process of reaching the end portal much easier.
If you know a world well from survival mode, you can use its seed (or the "Re-Create" button) to take advantage of that knowledge in hardcore mode.