Q&A with the Seat Expert

I assume that you are flying on Northwest Airlines, in which case booking class T is a deeply discounted coach class, while Q is slightly more expensive. Airlines have different order for their booking classes, and have different policies for upgrades. As for Northwest,  booking class is reportedly the third tie-breaker for upgrades, so it might not make much difference. The first tie-breaker appears to be your frequent flyer status on Northwest, and the second tie-breaker is the amount that you spent on the airlines in the previous year.