Beginning the pool construction process and have found that the very few contractors who install vinyl pools are quoting approx. 50% less than quotes we have received for the same size guinite. Is there a reason(s) to avoid vinyl in this area- Alpharetta, GA north of Atlanta? Clay soil issues? Water table issues? The price difference is so substantial, I want to make sure I am not making a huge mistake if I decide to install a vinyl pool. Thank you.