Reading Shin Kanzen Master N3, there is a chapter on comparisons, which includes 対して、反面、and 一方で beside each other. I've tried to piece together the difference between them, as they seem quite similar but not interchangeable. Below are my understandings and example sentences that I produced to illustrate my understanding. Feedback is much appreciated!
It seems like 対して is a non-judgmental contrast of two different subjects based on one shared aspect;
Xさん：I've heard of Author A. Doesn't he write action novels?
Yさん：He usually writes action, but his latest is a crime novel.その作家はほとんどアクション小説を書くのに対して、最新の小説は犯罪小説だ。
反面 is a judgmental contrast (ie there is a clear positive and negative) of two aspects of the same subject:
Xさん：What do you think of Author A?
Yさん：He writes good crime novels, but his actions novels are boring.その作家は面白い犯罪小説を書く反面、アクション小説がつまらない。
一方で underlines the existence of different aspects of the same subject, which may or may not conflict with each other.
Xさん：I don't want to read Author A, he only writes action novels.
Yさん：He does write action novels, but he also writes crime novels.その作家は確かにアクション小説を書く一方で、犯罪小説も書く。
by it_ribbits