Many are concerned about the high RAM usage of ESET's products but fail to perhaps understand why this maybe the case. Consider the specifications of a mechanical hard disk drive, in particular the "latency", typically measured in milli-seconds(ms) order of magnitude 10^-3. Now consider the latency of RAM measured in nano-seconds (ns) order of magnitude 10^-9.
Clearly we see that the latency for RAM is 1,000,000 (10^6) times less than that of mechanical HDD, essentially indicating that RAM works at a rate one million (1,000,000) times quicker than slow mechanical HDDs. Many who own solid state drives will notice a HUGE performance increase in loading times of applications.
Now if an application such as ESET's offering loads its signatures into RAM of course the overall memory usage of the process is higher but the process has exceptionally quick access to the signatures (information) it seeks. If the signatures were not loaded directly into RAM and the process was required to page to hard disk drive for the signatures (information) then obviously this would impact performance negatively which, is essentially what most other antimalware applications do. (Plus vendors use tricks to hide memory usage in virtual memory, page file etc)
Most ESET user's will state how "light" the application is which, is testament to the optimisation of the product. Also, how many antimalware programs scan ALL files by default real-time with minimal impact on computer performance? Take Avast for example, it is considered to be "light" yet to achieve this it is restricted to only scanning a default set of files real-time. Change this option to scan ALL files real-time and watch how negatively it impacts your computers performance. It is not well optimised.
For these reasons i stick to ESET along with its stellar low false positive rates.