Comodo Total Definitions:19014866 19M
Norton (symantec) Total Definitions : 18,799,347
Comodo > Symantec
1. There are a marketing issue involved. Companies estimate the number of viruses by high.
2. There are different counts possible: variants, etc.
3. There is not an international rule for virus naming, so same virus could be consider one or more by other company.
4. Scanning settings are very important.
5. Active viruses (ITW) are really more important then the whole number.
6. Generic signatures and heuristic detections cannot be really counted as 'virus detection'.
Well, etc. etc.
In fact, this was posted in the past:
The reason why the definition count is decreasing: Comodo is making each definition more efficient at detecting malware; therefore, less definitions are needed to detect each malware variant. Comodo is adding new detections regularly (see update page), so Comodo's ability to detect malware is increasing even though the number of definitions is decreasing.