Is there a difference between the $20 and +$50 versions? I’m looking to get one, but was wondering why there’s such big price gap.

Here’s one for $20: http://www.amazon.com/BAFX-Products-…

Then there’s this one for $70: http://www.amazon.com/ScanTool-42720…

From what I can tell the difference is that the expensive one comes with its own app. If the difference is the type of app, what are some that you guys recommend? Also should I look into the free versions as well?