Let me restate my opinion from some pages ago:
a)Phonologically it is not in question that Spanish and Italian are closer. It is often easier for an Italian to understand Spanish than several minority (Romance) languages of Italy.
b)Regarding the written language I would say that instead it is easier to understand French, not just because the vocabulary is closer but also, as I experienced, because in French there are much fewer false friends. And this is not just an impression since, as Ipse showed us, lexical analysis also points in this direction.
Overall this for me is quite, how can I say it... irrelevant. But I would be forced to lie if I neglected any
of the two points above. Moreover, if I were able to choose whether I wished that Italian was more close to Spanish or French overall, I would definitely pick the former because I find it nicer. But I can't do much about it.
Honestly I think also that it is quite strange that a weird Romance language spoken so far in the North is written in a manner that is very close to Italian. If we spoke about Occitan then it would make more sense, but the speech of Paris? How has this happened?
My impression is that until the XVI century Italian and Spanish were closer on all levels, probably also thanks to the prestige status of Spanish and Italian at that time.
Then from XVII century up until recent times this changed completely and many Italian intellectuals and writers used French extensively, sometimes even more fluently than Italian itself!
I refuse to think that this has not left any track in Italian.
And do not think that Italians liked it, since I read that in the past Italianists carried out the ruthless epuration of the construction venire
+ infinite, used to express a very recent past, from any form of vernacular and literary Tuscan, because it was suspected of being "a dangerous French influence". And more recently in high school I had an old teacher of Art History who corrected "dettaglio" in all our tests as an "incorrect French borrowing". In fact according to him we had to use the more Italian "particolare".
Regardless I am tired of cherrypicking so I took the map above from Wikipedia which seems me fine, at least according to my non-professional knowledges. I also liked that they use the term "South Italian" as the primary name for South Italian vernaculars, relegating the confusing Neapolitan to a secondary role. The map seems nice to me also because it shows how "distant" are the different Romance languages. So one can see that Tuscan, and therefore Italian, is reletively close to Western Romance languages in comparison for instance to the other Italo-Romance ones; but it is also possible to see that despite these influences it still belongs to a different branch of the Romance family.
So combining this with the two points above all what I can honestly say to answer the initial question is only: neither Spanish nor French is truly closer to Italian