I guess the next question is:
Is there a reasonably priced app in the app store that matches 7-zip capability?
Thanks.
None. There is no OS X app which gives you the choice of 7z compression methods (LZMA, LZMA2, PPMd, BZip2), dictionary size, word size, solid block size, CPU threads.
SmartZipper Pro does provide the full Compression Levels (Store, Fastest, Fast, Normal, Maximum, Ultra) and allows the creation of solid archives, whereas BetterZip and Entropy do not. BetterZip and Entropy just gives you some fuzzy compression levels (None, Slow, Normal, Fast), but have better support for drag and drop than SmartZipper Pro.
You'll just have to play around with all the apps and see which one is satisfactory for you.