前一段用 on the one hand,后一段最好用 on the other hand,但也有人用别的词来代替,比如:On the one one hand we must clean up the city,but we must also eradicate poverty.
前一段没有on the one hand,后一段可以有on the other hand.
比如：I would really like to go for a long walk tonight.On the other hand,there's still lots of work to be done.
这样的句型 on the one hand,on the other hand 都需要：
There is a political struggle going on with A on the one hand and B on the other.
I hope this is enough evidence for you.