what difference between Disk Basic vs Disk Enhanced ??

In my experience, the difference is that Disk Enhanced never works.
But yeah, I’ve been wondering the same thing myself. The compatibility section will tell you that Disk Enhanced has additional requirements, but as far as a functional difference, I’ve seen no answers from anyone on this.

One thing I’ve noticed is “enhanced” uses mod_rewrite rules (it writes to your .htaccess), while “basic” does not. I assume basic serves directly from PHP which probably wouldn’t make it as fast as enhanced, but I’ve not noticed a difference.

Also, the “enhanced” file cache directory structure is different (more elegant) than basic’s:
/wp-content/w3tc/pgcache

I’ve used enhanced, but switched to basic in order to get some of my redirects, which were failing, to work.