Both sonatas are notable in the day to day sense of the word, but the article on Reubke's sonata, (I'm assuming you are referring to this?) establishes its notability by including significant sources on the subject. In this case an issue of The Musical Times as well as the publication of Julius Reubke (1834-1858), notes to Kevin Bowyer's recording of The 94th Psalm. You just need to find some published works that discuss the sonata and then the article can be published into Wikipedia. See the golden rule.   Talk to me!