I voted based on your example. I thought that was an actual possibility. If you only have a Het Pied girl, and a Pied and Pastel Het male, I would do the Pastel Het to Het (in an attempt to hit the Pastel Pied). However, in the event of your example, I would do the Pied to Pastel Het (vs. Pastel Het to Pastel Het), as I would want a better shot at Pastel Pieds. Then the following year you could put the Pastel Pied to Pastel Het to up your odds at Super Pastel Pieds.
I did something very similar this past year. I had a Pastel Het Pied girl that was ready. My choices were Pied male or Pewter Het. While the Pewter Het could have given me some cooler stuff, I wanted to try and up my odds on getting a Pastel Pied to replace my regular Pied male. So I went with the Pied male. Now, I did get lucky in another clutch and made a Cinny Pied male that will probably see the Pastel Het girl this year.
I hope that helps,