Rossini and Weber are both second rank composers who are both firmly in the operatic and orchestral repertoire - and both are on the 'light' side of classical music. Both are, let's say, about equal in quality.
I very much like them both. But which do I prefer? The answer is Weber.
Rossini is probably a better composer, in the sense that he is effortlessly fluent, a fount of melody, a sparkling orchestrator. He also wrote the one genuinely funny opera (Barber of Seville).
By contrast there is something lumbering about Weber, his music is all angles and effort. His one repertory opera - Der Freischutz - is the best romantic opera in the German tradition (which means it is the best of all) - and yet it contains no really first rate arias.
And yet. There is something fresh, genuine and earnest about Weber - something clean and honest - that is beyond Rossini.
In Rossini there is no friction - it all slides-past like greased lightning!
I find that I value Weber for the fact that he contains so much resistance which he must then effortfully overcome.
In the end, it is a temperamental thing: the two great European characters - Latin and Northern. My preference is firmly for the Nordic over the Mediterranean; for the forest over the beach. I am somewhat jealous, somewhat resentful of the Southern ease and comfort and style - but it does seem rather shallow, rather glib.