Having a specific subreddit affords the ability to:
- Curate the content presented. It's not everything I've ever posted to Reddit, it's a specific set of interests. Visiting via the "old" view shows those topics, visible at the Internet Archive presently: <https://web.archive.org/web/*/https://old.reddit.com/r/dredm...>
- Style the subreddit, as noted.
- Provides other subreddit-specific features including the Wiki (which I'd made heavy use of), moderation tools, and the like.
TL;DR: It's different in many ways.