large number? Reddit has seen by far the most growth after switching to the new UI. The old reddit has already not been maintained to support new features such as polls.
Subreddit moderators get per-platform (old/new reddit.com, official mobile app, third-party mobile app) stats and all that I've seen share those numbers indicate new reddit.com is minority, old.reddit.com is basically invisible, vast majority is mobile apps. Of course it will be highly subreddit dependent.