They are completely different.
Convert It Mac is a program to Browse, Convert, Use on a Mac and Colorize designs. Visit http://www.MacEmb.com
to see the details. Because it runs on Mac only, it is not covered extensively at the Embrilliance website.
There are some tasks that virtually all embroiderers want to do and those things should be easy, inexpensive, simple and intuitive!
These are called “Essentials”.
If you want to combine designs; form scenes with overlapping designs; re-size designs and recalculate stitches; add Multiple Lines of Lettering; Add Monograms in many styles; change colors; print templates; change thread brands, Convert between formats, Look in Zips
or simply watch your designs sew onscreen, then Essentials is for you!
Essentials has its own page, http://embrilliance.com/embrilliance-essentials
so you can see the features.