R620 - iDrac7 - Which version? 1.66 vs 2.20

So I'm updating the base software on some of our servers and have a question.  When I view the downloads page for my R620 server, I see two options for the iDrac software.

DELL iDRAC7 1.66.65

and

iDRAC with Lifecycle Controller v. 2.20.20.20

What's the difference in these downloads?  Do both update the iDrac itself or is the second one just the lifecycle controller?  Why would I want the 1.66 version over the 2.20 version?

Or maybe I'm just reading this completely wrong.

Thanks!