The QaCONNECT REST Client only allows you to remotely trigger tests in batch/bulk easily and rapidly and most importantly w/o having to do any programming to integrate w/ our QaCONNECT REST APIs. 

The QaCONNECT REST services will allow you to do more than schedule/trigger executions remotely. They will allow you to inquire upon the tests scheduled remotely (or scheduled manually within Worksoft SaaS), to stop (abort) executions remotely, and to get list of executions done within specific time period or by a specific user, and to download test results, etc. But you have to develop code that makes calls to the new QaCONNECT REST API. 

QaCONNECT REST Client helps you NOT have to program/develop code to make use of QaCONNECT REST API but gives you reduced functionality.

QaCONNECT REST API gives you more functionality but requires you to program/code.