In and A are both fine although Italians tend to use A for the months, IN is rarely if not ever used when referring to months. IN is mainly used with the seasons (from my experience). Both mean the same thing and will get the message across, but you will get pointed out quicker of being a person who learned the language imo. Just like Ma and Bensi; Ma is used in everyday use, Bensi is hardly ever used unless speaking in an extremely formal setting. This sentence above is correct although "Non AD aprile, ma AD ottobre" would sound more natural. Ciao amici italiani
Technically all three are correct,and they depend on the region of the speaker. In everyday usage you will mostly see 'ma'. 'bensì' is a bit formal/old fashioned and 'piuttosto' is.. well... long. Nowadays it is used a lot in the (frequently misused expression) expression 'piuttosto che'.
IaisSimon: "in" is simply the preposition whereas forms of the preposition + the definite article ("the") will result in the combinations you're asking about. So nel < in + il; nello < in + lo; nella < in + la; negli < in + gli, etc. So it'd be : in citta' but nella citta' (depending on how you're using that phrase).
A request for DL - please be consistent with mispellings/typos. I mispelt October, adding an extra "B", this was moarked wrong saying I used the wrong word -what else could "Octobber" be!!!. At other times, similar errors are passed with a note highlighting the mispelling. Consistency PLEASE