Both of them are very good boards - the Z87 will be slightly cheaper, the Z97 will allow you to upgrade to the Broadwell chips when they're released without needing to upgrade the board. They're almost identical in features, but the Z97 supports M.2 and eSATA.
The other boards are good too - which one is best depends on your budget, which features are important to you, and how you intend to use it.