Learnability Versus Comprehensibility
Esperanto and Interlingua are fundamentally different in their purposes. Whereas Esperanto is meant to be an international second language able to be fluently learned by speakers of any language, Interlingua is directed more toward European languages, especially its control languages. Though Esperanto may be more neutral as well as easier to master, Esperantists can usually only communicate with other Esperantists; Interlingua, however, can be understood well by a speaker of any Romance language (as well as sufficiently educated speakers of other European languages, especially English).
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