French, most definitely. Pronunciation is probably the hardest part of learning French.
That's funny, because I have always thought that French was kinda easy to pronounce, for an English speaker. Now, if you are reading French aloud, yes they have a very peculiar sound system compared to English, but I have never had any trouble mimic the sounds of French... and I don't mean mocking the sounds, either. I've actually had many people mistake me for someone who is a fluent, when I actually don't know any of it, except a very basic words, and the English-French cognates.
This could possibly vary for an English speaker, based on dialect differences. Where I am from, we use alot of soft sounds, and diphthongs, in our speech, so it might just seem more natural to me than the "rapid fire consonants" of Spanish.
Edit: I meant to say "monothongs" meaning the we monothong things where in most other parts of the country they are diphthongs.
I also find French to be very easy to pronounce. However, I have known several people who after a year of taking French couldn't even pronounce their vowels. I try not to give the typical English speaker too much credit, you see.