Listen to the teacher, (like you never heard that befor) that is the only advice someone can truly give. If you sell them, someone will buy them, almost at any price you ask on the Bay.
But you have to decide what is more important, the current Stangs, or the desired White's. Both are a solid choice.
I too understand the choice is tough, I have always had to sell toy cars to buy more toy cars throughout the years. But with very few exceptions, I have always been pleased with my choice. And after 25 years of adult collecting, that's a pretty good track record!
Good luck. And if you decide to sell, make sure you post the link and info on the HT auction board. Lots of Mustang guys would like to check that one out!