Having studied both German and Spanish, I believe that Spanish is easier for the native English speaker than it is for the native German speaker.
The hardest thing in Spanish is the verb system. German helps here a little because of the inflected personal forms; native English speakers have trouble getting use to so many inflected forms. On the other hand, English is helpful, because Spanish uses a gerund form similar to English and uses the present and past participle forms pretty much like English. But neither language helps much with the really hard things about Spanish verbs:
1) the two verbs that mean "to be" (ser and estar),
2) the choice of two past tense forms, and
3) the frequent use of the both past and present subjunctive.
The noun system is relatively easy for English speakers to adapt to, since one has to choose between masculine and feminine nouns, articles, and determines. Because there is not neuter, the English speaker has no temptation to use natural genders when referring to inanimate objects (which is a problem when we learn German). Moreover there are no case declensions, which is similar to English. Plus the genders are largely determined by the final vowel (o or a), so learning the genders is not too difficult. So I don't think that the German noun system provides a big advantage in learning the Spanish noun system.
Vocabulary-wise, English speakers have a big advantage because so many words in English are latinate in origin. So the number of cognates is quite high, especially in professional vocabulary.
Germans also seem to have trouble with long Spanish words. You may laugh about this, but I took a Spanish course at a German University and the German students complained about how long Spanish words are. I almost died laughing. But in a sense, they were correct. Long German words are built up from relatively short words that are "glued" together. If one recognizes the component words, it is often easy to grasp the meaning of very long compound words. In contrast, a lot of Spanish words are longer than the base words in German. Nonetheless, I never heard English speakers complain about long Spanish words.
Regarding pronunciation, German may offer some minor advantage in that German vowels are generally not deformed by dipthongs. Since long English vowels are dipthongs, English speakers have some trouble purging the dipthong and pronouncing a pure vowel. I don't think either language has much advantage when it comes to consonants.
For what its worth, that's my take on this question.