There is no single authoritative total that cleanly counts all Jain books in Gujarati vs Hindi, so I can’t say this with absolute certainty. But based on major Jain book catalogs, Gujarati has a very large and long-established Jain publishing tradition, and in practice it is often the stronger language for Jain book output. Hindi also has a huge Jain book corpus, especially in modern educational and devotional publications. ( jainonline.org)

So, if you want the most balanced short answer: probably Gujarati overall, though Hindi is also very extensive. ( jainonline.org)