They have a bigger take-out rate, and they also have an interest-bearing loan product. However, Affirm credit losses are higher. Their prospectus doesn't mention the NTM, but I'm sure it could be worked out. The big take-out rate, combined with their larger losses, exposes them to the competition hitting the sector.
I found this below in the Affirm prospectus - it shows active customers at 3.88m at Sep-20, up only 63% from a year ago, Active customers are about double Sezzle. Transaction per active customers is only 2.2 - very weak - customers are not engaged with the product.
Sezzle is the one with the sustainable, scalable business model loved by customers and merchants.
https://www.sec.gov/Archives/edgar/data/1820953/000110465920126927/tm2026663-4_s1.htmI think we're in for a good month here!