What is the talk like between Ben Winthrop and Mr. Macy in Silas Marner?

It looks like you may be referring to the conversation at the Rainbow in chapter 6. That is the only evident instance when both Mr. Macey and Ben Winthrop participate in a conversation. Yet, Ben Winthrop and Mr. Macey do not directly address each other in this group conversation at the Rainbow.
Rather, they team up to tease Mr. Tookey by throwing out individual insults at the poor deputy clerk. During the conversation, Ben Winthrop (a wheelwright and the leader of the church choir) draws attention to Mr. Tookey's inability to carry a tune.
For his part, Mr. Tookey is insulted and demands proof of his supposedly inferior singing abilities. He asserts that there is always bound to be two opinions about something.
At this point, Mr. Macey makes a patronizing comment. He tells Mr. Tookey that he is indeed right and that "There'd be two 'pinions about a cracked bell, if the bell could hear itself." Mr. Macey's comment is rather insulting because it suggests that Mr. Tookey is like a "cracked bell" who can't hear how bad his singing is.
Of course, Mr. Macey's comment causes everyone to laugh at Mr. Tookey. Upset at being ridiculed, Mr. Tookey argues that it was Mr. Crackenthorpe who asked him to fill the position of parish clerk and that this position comes with the right to sing in the choir. At this, Ben Winthrop continues the refrain about Mr. Tookey's poor singing abilities:

"Ah! but the old gentleman and you are two folks," said Ben Winthrop. "The old gentleman's got a gift. Why, the Squire used to invite him to take a glass, only to hear him sing the "Red Rovier"; didn't he, Mr. Macey? It's a nat'ral gift. There's my little lad Aaron, he's got a gift—he can sing a tune off straight, like a throstle. But as for you, Master Tookey, you'd better stick to your "Amens": your voice is well enough when you keep it up in your nose. It's your inside as isn't right made for music: it's no better nor a hollow stalk."

Ben Winthrop's insulting comment leads everyone to conclude that he has bested Mr. Macey's "epigram" earlier about Mr. Tookey being a "cracked bell." So, the talk between Mr. Macey and Ben Winthrop can be said to be conspiratorial and sarcastic in nature. Both men team up to insult the harassed Mr. Tookey.