86400 supports all three phone payment options (Google Pay, Apple Pay, Samsung Pay) whereas Up doesn’t support Samsung Pay. I have a Galaxy watch that only works with Samsung Pay, so I switched to 86400. Probably not a primary consideration for most, but a difference all the same.
No Pay ID for most neobanks yet either. But for most people, you’ll probably need to retain a regular bank for over the counter options like banking cash etc. and can link PayID to that.