Try city-data.com for general info. DTW is cheaper, MEM is warmer. The flying seems to be better out of DTW though, and I'll let someone else tell you about the "fishbowl" in MEM...

As for all the questions about "how fast can I upgrade" the most junior guy to get upgraded on the last award has been here almost a year and a half. DISCLAIMER: Results not typical, your results may vary. These statements have not been evaluated by the FDA.