Put yourself in the position of your business partner who receives an e-mail. The text in an e-mail is highly unstructured. You first have to read why and where he wants to meet, and you have to manually compare the date proposals with your calendar. Until your business partner decides to use Scedule for free, he certainly has to do it himself.
But with Scedule he receives a structured and professional invitation with all relevant information such as the answers of the participants. And the dates suggested are already coordinated internally (among Scedule users) so that he has a free choice, and the risk that you would have to postpone the meeting because of internal cancellations, is limited.
In addition, you can decide to brand the smart Invitation in the look and feel of your company, so send it in an appealing design.