When Oliver Cowdery was copying from 𝓞 into 𝓟, he initially wrote “speaketh unto another”, probably because he had just written “spake unto me”. He soon corrected his error (with no change in ink flow) by crossing out the unto and supralinearly inserting with. Although the text overwhelmingly prefers “to speak unto someone” (256 times), there are six occurrences elsewhere of “to speak with someone”. The preposition to also occurs with speak; “to speak to someone” is also comparatively infrequent, occurring 18 times.
Summary: Maintain in 1 Nephi 11:11 the preposition with in “as a man speaketh with another”; although “to speak unto someone” is more prevalent, “to speak with someone” also occurs in the text.