I think it really depends about what we mean by "guaranteed delivery". If you are more interested in the infrastructure and consider each piece as a different p

I think it really depends about what we mean by "guaranteed delivery". If you are more interested in the infrastructure and consider each piece as a different part then yeah, hop-to-hop reliability is important to you and you want XEP-0198. That's like "guaranted delivery of a packet". If however you are more interested in the application that sits on top of the infrastructure, then what you really care about is whether the recipient did receive your message: that's XEP-0184. That's more like "guaranted delivery of a message". Of course both are complementary (and to me both should be implemented)