Piano Teq Play vs. Standard

I recently stumbled across piano teq through a fellow piano player. After hearing some samples on line, I downloaded the trial version about 4 times in row, disappointed every time when the session timed out. Amazing feel and response, more so than any other piano software I've played.

My question is what is the main difference between play vs standard? Based on what I've read from their website, does the placement of microphones make a huge difference in the tonal picture?  Also, if I purchase "play" and up-grade to "standard" in the future, will I have the full standard version or will there be any limitations?

I'm excited about owning piano teq soon!