There have been very few comparative tests of the Comodo Antivirus component, as it is only 6 months since the program was first released. There is a recent one here:
http://malwareresearchgroup.com/?page_id=2
When this test was carried out the database had over one million fewer signatures.
For Comodo the antivirus is not such an important part of their protection, as they are far more focused on prevention.
It has been said that the HIPS component is too difficult for beginners, but in the latest version 3.9 of Comodo Internet Security there are very few demands on the user. This version is now at release candidate stage and should be released for general use very soon now.
Of course the great thing about this program is that it is free for everyone.