Before you buy software, you need to know what you need from the software. Some have good graphs of IV vs. HV. Others while lacking the former may have good scanning abilities. Other web based ones have great scanners but non-existent greek whatif analysis. After trying 3 of the major ones, the best combination I found with good greeks, scanners is a now-defunct company called Bay options. The developer quit the business, so the remaining ones are optionvue-nice program but expensive, ivolatility.com, optiontree.com, optionpro by essextrading, optrack by track data, the plug in for AT financial. Good luck