PDFs are hard to read on phone. The abstract page is better if you just want to read abstract. Some PDFs can also contain large images, which is again bad for mobile if you only really wanted to read abstract.

Also from the main Arxiv page, you can click on the links to each of the authors, see the version history, etc

The HTML page takes an order of magnitude less time to load than the PDF (1 vs. 8 seconds) on my phone.