It depends what you mean by "easier." First of all, why are you looking for "easy" (does he have special needs, for example)? Secondly, I'm curious about why these are the only 2 choices. Is there no room in any classes but those? Or has he felt forced into a corner and those are the 2 he has latched on to? What are his reasons and motivations? Kids learn better when they want to, but you're seemingly asking for something simple. I'm not sure if that's a general question because he has a heavy course load, or if he's got learning challenges or heavy activities. I'd have to know that before advising you further.
I major in Spanish, have used it in every job since college, and I tutor it to adults and college students (and an occasional high school student if the kid is there voluntarily and not because the parents are forcing it), Spanish is phonetic; French and German are not. The grammatical structure of the German sentences is tougher than that of Romance languages (Spanish, French, Italian, Portuguese, Romanian), although there are also some differences in English. And many would argue that they are easier than Russian, Mandarin, Hindi, Hebrew, Arabic or any other language that uses an entirely different alphabet.
Neither French nor German are spoken much in life outside the classroom, so there's virtually no opportunity for him to practice or see the relevance of the language. (ETA - I am editing this to clarify that neither language is spoken much in local communities in Florida, where you are. Of course, there are international opportunities for pretty much every language, in international business, the State Department/diplomacy, and more. But it's hard to practice in high school at that level. I was referring to immediate application in "real life for a teenager" and reinforcement outside the classroom during the high school years.)
Feeling that something is "pointless" doesn't much motivate a student to learn. Unless you have stores and communities in your area that are highly populated by German- and French-speakers, your son is going to have a harder time than if he learned Spanish.