Hey - I did both GCSEs and A-Levels in French and Spanish. They both have Latin derivation, so they certainly have many similarities and you'd see this when studying them. I think they have about 75% lexical similarity. I found learning about both cultures fascinating and it's even better when you get to actually visit the countries and speak with natives.
French and Spanish are both among the most widely spoken languages in the world. Spanish is the fourth most spoken language, spoken by approximately 538 million people, and French is the fifth most spoken language in the world, with around 276 million speakers. So this is certainly advantageous in terms of job prospects.
In terms of ease, it depends. I found French and Spanish quite easy to learn together because of the lexical similarity. However, for someone else, this could be the cause of confusion. E.g. "homme" in French and "hombre" in Spanish (both meaning "man") or "entrer"/"entrar" (both meaning "to enter"). It also depends on how much you want to be challenged. French grammar is slightly easier than German I believe. I suspect the same with Spanish.
Honestly, it's a very personal choice. Have a listen to each language, in both spoken form and also musically. Look into the culture, maybe even some literature if you find that important. Learn a little bit of the grammar to begin with. Formulate an opinion. This will help you get a glimpse of what the language study will be like before fully committing to it. I much preferred French and Spanish phonology to that of other languages, like German, for example. Hope this helps.