Neck and neck 不相伯仲

So close that the advantage or lead shifts from one to the other or is virtually indistinguishable. The term comes from horse racing, where the necks of two horses in competition appear to be side by side

eg: The two are neck and neck in developing a new operating system for the computer

Neck and neck的意思是二者十分相近，不分上下。最初源于赛马，形容两匹马并驾齐驱不分前后。

例：二人都在开发新电脑操作软件，不相伯仲.