At the end of Freedom’s Progress you’ll have the choice to keep hold of Veetor and send him to Cerberus or you can let him go with Tali.
Choice: Send Veetor with Tali or Send Veetor to Cerberus
At the end of Freedom’s Progress, you’ll find Veetor, and Tali will tell you that he needs medical attention, and asks you to let him go back with her. Here, you’ll get the chance to send Veetor to Cerberus for interrogation or let him go with Tali.
Send Veetor with Tali
If you decide to send Veetor with Tali, he can play a significant part in Tali’s loyalty mission: Treason. He is one, of two parts required to give you another choice in said mission.
Send Veetor to Cerberus
Not a lot of good comes out of this. Veetor can still be found on the Migrant Fleet, but he’s not the same again, claiming mental torture from Cerberus, he will also be afraid to talk to you, and at one point, will even scream at you to stay away from him.