The biggest difference is that HTTP/3 (and to a lesser extent, 2) are designed and implemented entirely and exclusively for for profit-business use cases at the detriment to all other use cases and specifically longevity. Since there are no HTTP/3 implementations that allow the use of non-CA TLS or even just plain text that means in order to host a visitable website for major browsers you have to get continued re-approval from a third party corporation every ~3 months. This means that websites using HTTP/3 will have very short unmaintained lifetimes. HTTP/3 sites will not last many years. They'll simply become unvisitable in a fraction of a year if there's ever any problem in the huge chain of complexity that is acme2 (and when acme2 is deprecated and turned off a huge portion of the web will die, much more than died when acme1 was turned off on LE).
There is one feasible change that can be made now: Firefox needs to change the flags in it's HTTP/3 library build so that self signed certs are allowed.
There is one feasible change that can be made now: Firefox needs to change the flags in it's HTTP/3 library build so that self signed certs are allowed.