noun which may take the genitive case particle 'no'
much the same; nearly equal; neck and neck
Colloquial expression used when two things are so close that it's hard to tell which is better or ahead; often implies a tie or dead heat.
二人の実力はおっつかっつだ。
Their abilities are about the same.
この二つの案はおっつかっつで、どちらがいいか決められない。
These two proposals are neck and neck; I can't decide which is better.