How to determine what IV is the best predictor of DV? Advice appreciated

I work in real estate. I am trying to determine what quantitative characteristic is the most reliable indicator of sale price. In other words, in commercial real estate, should I determine value based on square footage or on sales volume?

As a noob, I thought that simply comparing coefficients of variation would be a good bet. I was also considering a log-log model (IV should be close to 1 if we have a linear relationship, I think). However, I'm open to more complex methods of determination. Thanks for the help.